# Estimation and Comparison of Immunization Coverage under Different Sampling Methods for Health Surveys

Authors: D. C. Nath; B. Patowari
Journal: International Journal of Population Research
 (2014)

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## Abstract

Immunization currently averts an estimated 2-3 million deaths every year in all age groups. Hepatitis B is a major public health problem worldwide. In this study, the estimates of hepatitis B vaccine coverage are compared among three sampling plans namely,30×30 sampling and 30×7 sampling method under cluster sampling and systematic random sampling schemes. The data has been taken from the survey “Comparison of Two Survey Methodologies to Estimate Total Vaccination Coverage” sponsored by Indian Council of Medical Research, New Delhi. It is observed that the estimations of proportions of this vaccination coverage are significantly not different at 5% level of probability. Both 30×30 sampling and 30×7 sampling will be preferred to systematic sampling in estimation of hepatitis B vaccine coverage for this study population because of quick estimation and lesser cost. The 30×7 cluster sampling is the most recommended method for such immunization coverage especially in a developing country.


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## Body

## 1. Introduction

World Health Organization states that trends related to global vaccination coverage (global estimates for 2008) continue to be positive [1]. Immunization has been one of the greatest public health successes. As many emerging and reemerging diseases are now the significant contributor to childhood morbidity and mortality, hepatitis B is one of them [2]. Hepatitis B is a liver disease caused by the hepatitis B virus [3]. It is a disease with high prevalence, severe morbidity, and premature mortality. It is highly infectious and can spread rapidly in the population through asymptomatic carriers [4]. About 78% of global pool of hepatitis B virus infection is from the Asian countries, particularly the developing countries of Asia-Pacific region [5]. Medical and public health experts strongly support universal vaccination against the hepatitis B virus, but many parents still do not think that their children need to be vaccinated. The hepatitis B virus is 100 times more infectious than the HIV virus [6]. The carrier rate of hepatitis B in India is different in the different regions of the country. The overall carrier rate is often quoted as being 4.7% [7]. Thus, India is an intermediate to high endemicity country [4].Since 1982, hepatitis B vaccine has been available to prevent hepatitis B virus infection [8]. Hepatitis B vaccine was given within 12 hours of birth, then at 6 weeks and at 14 weeks [9]. This is to be noted that the children of Assam in the North-East Region of India have consistently evidenced low rates for routine childhood immunizations. Lack of information among the parents was one of the major causes of dropout of vaccinations [10].In the late 1980s, the World Health Organization (WHO) developed the Expanded Program on Immunization (EPI) survey methodology also known as a two-stage (30 × 30) cluster sampling (recommended by WHO), which has been widely used ever since to assess vaccination coverage. Immunization status of children was evaluated using WHO-30 cluster methodology [11–14]. In this study, the estimates of hepatitis B (at birth) vaccine coverage are compared by using two-stage cluster and systematic random sampling method. The main objective of the study is to make a comparative study of hepatitis B (at birth) vaccine coverage between (i) two-stage cluster (30 × 30) and systematic random sampling and (ii) two-stage cluster (30 × 7) and systematic random sampling. Also costs of surveys of these three methodologies have been compared.


## 2. Methods

The data for this study has been taken from a survey (conducted in 2011) “Comparison of Two Survey Methodologies to Estimate Total Vaccination Coverage” sponsored by Indian Council of Medical Research (ICMR), New Delhi. The data has been collected during the period from January to October, 2011.


### 2.1. 30 × 30 Cluster Sampling Method

In this method, the population needs to be divided into a complete set of nonoverlapping subpopulations, usually defined by geographic or political boundaries. These subpopulations are called clusters. In the first stage, 30 of these clusters are sampled with probability proportionate to the size (PPS) of the population in the cluster. Sampling with probability proportionate to size allows the larger clusters to have a greater chance of being selected. The clusters are sampled without replacement. In the second stage of sampling, 30 subjects are selected within each cluster. Although the sampling unit is the individual subject, the sampling is conducted on the household level.


### 2.2. 30 × 7 Cluster Sampling Method

The 30 × 7 cluster sample was developed by WHO in 1978. The goal of this sampling design was to estimate immunization coverage within ±10 percentage points of the true proportion, with 95% confidence. It is also a two-stage cluster sampling where in the first stage 30 clusters are selected and thereafter in the second stage 7 units are selected within each cluster [15].


### 2.3. Systematic Random Sampling

Systematic sampling is a random method of sampling in which only the first unit is selected with the help of random numbers and the rest get selected automatically according to some predesigned pattern. If the population sizeN=nk, where n is the sample size and k is an integer, and a random number less than or equal to k be selected and every kth unit thereafter. This procedure is linear systematic sampling. When N≠nk, then every kth unit should be included in a circular manner till the whole list is exhausted; which is known as circular systematic sampling.The questionnaire has been developed to collect information of household details like type of family, source of drinking water, purification of drinking water, toilet facility in the household, fuel used for cooking, number of household members, number of eligible members (the children of age from 6 months to 5 years), number of earning members in the household, and approximate monthly household income; information of the eligible members regarding record of vaccine and place of vaccination is collected. The vaccination coverage of hepatitis B at birth is considered.The survey is conducted in Guwahati, the capital city of Assam. To get the idea of geographical location of Guwahati city, the ward map of the city has been collected and a listing of its wards from Guwahati Municipal Corporation (GMC) gives a lot of idea about the proper location of different wards of the city. And the listing of its wards gives the information about the number of assesses per ward. The city is comprised of a total of 60 wards. Out of 60, 30 wards are selected where selections are being made with the help of random number table (Table1).Table 1
Selected wards with area and total assesses.
Sl number
Ward number
Area
Total assesses
1
2
Jalukbari
1585
2
4
Near Pandu Colony Road
570
3
5
Gar Pandu
3094
4
9
Kamakhya Railway Station
44
5
11
Santipur
2768
6
12
Fatasil NC
5243
7
15
Udalbakra Grant
3450
8
17
Barsajai
1990
9
18
Bharalu
1971
10
24
TV Tower
2062
11
25
Ulubari
4185
12
26
Medical College Road
2655
13
33
Dighalipukhuri
1329
14
35
Chenikuthi
2950
15
36
Near Stadium
2721
16
37
Silpukhuri
2511
17
38
AIR
1723
18
40
Chandmari
1509
19
42
Opposite State Zoo
4027
20
43
Kachari Basti Road
3891
21
46
Guwahati Refinery
1330
22
47
Holy Child School
1125
23
48
Railway Colony
2397
24
50
State Zoo
2084
25
51
Hengerabari
5140
26
53
Sixmile
2073
27
54
Panjabari
2835
28
55
Beltola Bazar
2747
29
57
Rukminigaon
3855
30
59
Kahilipara
4664
31
60
Bhetapara
4674
Ward number 9 (Kamakhya Railway Station) is rejected as the ward list shows that the ward has only a total of 44 assesses.With the two-stage (30 × 30) cluster sampling method in the first stage 30 wards are selected and in the second stage 30 units from each ward are selected. For the selection of second stage units, a selected ward is divided into numbers of blocks such that the sizes of blocks are more or less of equal size. Also they are divided in such a way that the sizes of blocks are sufficient to draw the required numbers of sample. Then, one block is selected randomly and from that selected block we have collected the required number of sampling units (here it is 30 numbers of sampling units). Then, to select these 30 units, only the first household is randomly selected in a centrally located area of the block. After the first household is visited, the surveyor moves to the “next” household, which is defined as the one whose front door is closest to the one just visited. Where there are bylane in a particular lane survey procedure is carried out in that place according to the serial household number in that bylane. This process continues until all 30 eligible subjects are found. The subjects are chosen by selecting a household and for more than one eligible subject (children from 6 months to 5 years of age) in a household all are selected. This resembles random permuted block where the position of each unit is equally likely.After completing the 1st sampling method (i.e., two-stage (30 × 30) cluster sampling) in a ward, 2nd sampling method (systematic random sampling) is carried out in same ward. In this sampling technique, a random number is selected from random number table on the basis of the number of households in a lane where the survey was carried out in case of two-stage (30 × 30) cluster sampling and this became the first sampling unit (household) of the systematic random sampling. After that, each household is selected at an interval of 10 households continuing the process until the 30 sampling units are not completed. Here, the interval of household is taken as 10 so that the interval is neither too small nor too large. If we take the interval too small, then we should get so many repetitions of the samples from two-stage (30 × 30) cluster sampling which results in the same sampling unit in the 2nd sampling method (systematic sampling) and if we take the interval too large, then there should not be any relation between the two methodologies as the larger interval will cover larger area and both of the sampling techniques should take different places.


## 2.1. 30 × 30 Cluster Sampling Method

In this method, the population needs to be divided into a complete set of nonoverlapping subpopulations, usually defined by geographic or political boundaries. These subpopulations are called clusters. In the first stage, 30 of these clusters are sampled with probability proportionate to the size (PPS) of the population in the cluster. Sampling with probability proportionate to size allows the larger clusters to have a greater chance of being selected. The clusters are sampled without replacement. In the second stage of sampling, 30 subjects are selected within each cluster. Although the sampling unit is the individual subject, the sampling is conducted on the household level.


## 2.2. 30 × 7 Cluster Sampling Method

The 30 × 7 cluster sample was developed by WHO in 1978. The goal of this sampling design was to estimate immunization coverage within ±10 percentage points of the true proportion, with 95% confidence. It is also a two-stage cluster sampling where in the first stage 30 clusters are selected and thereafter in the second stage 7 units are selected within each cluster [15].


## 2.3. Systematic Random Sampling

Systematic sampling is a random method of sampling in which only the first unit is selected with the help of random numbers and the rest get selected automatically according to some predesigned pattern. If the population sizeN=nk, where n is the sample size and k is an integer, and a random number less than or equal to k be selected and every kth unit thereafter. This procedure is linear systematic sampling. When N≠nk, then every kth unit should be included in a circular manner till the whole list is exhausted; which is known as circular systematic sampling.The questionnaire has been developed to collect information of household details like type of family, source of drinking water, purification of drinking water, toilet facility in the household, fuel used for cooking, number of household members, number of eligible members (the children of age from 6 months to 5 years), number of earning members in the household, and approximate monthly household income; information of the eligible members regarding record of vaccine and place of vaccination is collected. The vaccination coverage of hepatitis B at birth is considered.The survey is conducted in Guwahati, the capital city of Assam. To get the idea of geographical location of Guwahati city, the ward map of the city has been collected and a listing of its wards from Guwahati Municipal Corporation (GMC) gives a lot of idea about the proper location of different wards of the city. And the listing of its wards gives the information about the number of assesses per ward. The city is comprised of a total of 60 wards. Out of 60, 30 wards are selected where selections are being made with the help of random number table (Table1).Table 1
Selected wards with area and total assesses.
Sl number
Ward number
Area
Total assesses
1
2
Jalukbari
1585
2
4
Near Pandu Colony Road
570
3
5
Gar Pandu
3094
4
9
Kamakhya Railway Station
44
5
11
Santipur
2768
6
12
Fatasil NC
5243
7
15
Udalbakra Grant
3450
8
17
Barsajai
1990
9
18
Bharalu
1971
10
24
TV Tower
2062
11
25
Ulubari
4185
12
26
Medical College Road
2655
13
33
Dighalipukhuri
1329
14
35
Chenikuthi
2950
15
36
Near Stadium
2721
16
37
Silpukhuri
2511
17
38
AIR
1723
18
40
Chandmari
1509
19
42
Opposite State Zoo
4027
20
43
Kachari Basti Road
3891
21
46
Guwahati Refinery
1330
22
47
Holy Child School
1125
23
48
Railway Colony
2397
24
50
State Zoo
2084
25
51
Hengerabari
5140
26
53
Sixmile
2073
27
54
Panjabari
2835
28
55
Beltola Bazar
2747
29
57
Rukminigaon
3855
30
59
Kahilipara
4664
31
60
Bhetapara
4674
Ward number 9 (Kamakhya Railway Station) is rejected as the ward list shows that the ward has only a total of 44 assesses.With the two-stage (30 × 30) cluster sampling method in the first stage 30 wards are selected and in the second stage 30 units from each ward are selected. For the selection of second stage units, a selected ward is divided into numbers of blocks such that the sizes of blocks are more or less of equal size. Also they are divided in such a way that the sizes of blocks are sufficient to draw the required numbers of sample. Then, one block is selected randomly and from that selected block we have collected the required number of sampling units (here it is 30 numbers of sampling units). Then, to select these 30 units, only the first household is randomly selected in a centrally located area of the block. After the first household is visited, the surveyor moves to the “next” household, which is defined as the one whose front door is closest to the one just visited. Where there are bylane in a particular lane survey procedure is carried out in that place according to the serial household number in that bylane. This process continues until all 30 eligible subjects are found. The subjects are chosen by selecting a household and for more than one eligible subject (children from 6 months to 5 years of age) in a household all are selected. This resembles random permuted block where the position of each unit is equally likely.After completing the 1st sampling method (i.e., two-stage (30 × 30) cluster sampling) in a ward, 2nd sampling method (systematic random sampling) is carried out in same ward. In this sampling technique, a random number is selected from random number table on the basis of the number of households in a lane where the survey was carried out in case of two-stage (30 × 30) cluster sampling and this became the first sampling unit (household) of the systematic random sampling. After that, each household is selected at an interval of 10 households continuing the process until the 30 sampling units are not completed. Here, the interval of household is taken as 10 so that the interval is neither too small nor too large. If we take the interval too small, then we should get so many repetitions of the samples from two-stage (30 × 30) cluster sampling which results in the same sampling unit in the 2nd sampling method (systematic sampling) and if we take the interval too large, then there should not be any relation between the two methodologies as the larger interval will cover larger area and both of the sampling techniques should take different places.


## 3. Statistical Analysis

Here, we estimate hepatitis B (at birth) vaccine coverage, demographic characteristics, and other health outcomes under both sampling methods. Chi-square test has been used to compare the results obtained from the two sampling methodologies. Tests for equality of two population proportions and 95% confidence intervals have been used to compare estimates under the two methodologies for hepatitis B (at birth) vaccine coverage. TheZ-statistic and 95% confidence interval for the difference of proportion are given as follows.The null hypothesis isH0:P1=P2 (i.e., there is no significant difference between the proportions of the number of children undergoing hepatitis B (at birth) vaccine of two methodologies)against the alternativeH1:P1≠P2.The test statistic is given by(1)Z=p^1-p^2p^q^[(1/n1)+(1/n2)],wherep^=x1+x2n1+n2,
where p^1 and p^2 are proportions of number of children undergoing hepatitis B (at birth) vaccine of cluster and systematic sampling, respectively. If |Z|>1.96, we reject our null hypothesis.The 95% confidence interval forP1-P2 is given by
(2)(p^1-p^2)-1.96p^1q^1n1+p^2q^2n2<P1-P2<(p^1-p^2)+1.96p^1q^1n1+p^2q^2n2.


## 4. Result and Discussion

Table2 presenting the demographic and health practices of the respondents shows that under 30 × 30 sampling scheme there is a significant difference between two-stage cluster and systematic sampling in case of respondents religion (P=0.02), source of drinking water (P=0.01), purification of water (P=0.00), and toilet facility (P=0.04). On the other hand, there is no significant differences between two-stage cluster and systematic sampling under 30 × 7 sampling scheme.Table 2
The demographic and health practices of the respondents under the two sampling schemes (figures in %).
Sampling procedure
30 × 30
P value
30 × 7
P value
Variable
Cluster
Systematic
Cluster
Systematic
Religion
Hindu
87.2
91.1
0.02
87.6
84.8
0.66
Islam
11.1
7.3
10.5
13.3
Others
1.7
1.6
1.9
1.9
Caste
General
75.0
71.6
0.18
72.9
75.2
0.84
SC
15.4
16.0
18.1
15.2
ST
3.2
4.8
3.8
3.3
OBC
6.3
7.7
5.2
6.2
Source of drinking water
Tap water
22.4
23.9
0.01
23.8
23.3
0.63
Tube well
5.8
3.9
5.7
4.8
Well
51.1
56.0
45.7
51.4
Others
20.7
16.2
24.8
20.5
Purification of water
Water filter
95.0
97.6
0.00
93.3
94.3
0.69
Others
5.0
2.4
6.7
5.7
Toilet facility
Sanitary latrine
93.8
95.9
0.04
94.3
92.9
0.55
Pit latrine
6.2
4.1
5.7
7.1
Fuel used
Kerosene
8.1
7.0
0.37
6.2
10.0
0.15
LPG
91.9
93.0
93.8
90.0The family related information of the respondents under the two sampling schemes (Table3) shows that more than 90% are living in nuclear family; that is, people prefer to live in nuclear type of family rather than joint family. Family related information has not shown any significant differences between two-stage cluster and systematic sampling under both (30 × 30 and 30 × 7) sampling schemes except for the age of mother (P=0.02) and the age of father (P=0.00) under 30 × 30 sampling scheme.Table 3
The family related information of the respondents under the two sampling schemes (figures in %).
Sampling procedure
30 × 30
P value
30 × 7
P value
Variable
Cluster
Systematic
Cluster
Systematic
Type of family
Nuclear
93.4
94.4
0.37
91.4
93.8
0.35
Joint
6.6
5.6
8.6
6.2
Monthly household income
Low
14.8
12.4
0.07
15.7
19.0
0.58
Middle
70.6
75.4
68.6
67.6
High
14.7
12.2
15.7
13.3
Age of father
20–30
7.2
5.0
0.05
8.1
7.6
0.97
30–40
73.4
78.0
68.1
69.0
40 and above
19.0
16.8
23.8
23.3
Education of father
No or primary education
3.1
1.4
0.00
3.3
4.8
0.43
High school
10.8
6.7
16.2
11.0
Matriculate
8.3
9.6
5.7
7.6
Intermediate
26.4
26.8
27.6
26.7
Graduation
44.3
49.2
39.5
44.8
Higher
7.0
6.3
7.6
5.2
Occupation of father
Govt. employee
20.2
21.0
0.69
22.9
18.6
0.72
Private sector employee
23.4
25.3
24.3
21.0
Business
30.6
29.4
28.1
33.3
Manual labour
10.1
8.2
10.5
11.9
Driver
4.9
5.3
6.7
6.2
Professional
10.8
10.6
7.6
9.0
Age of mother
15–25
8.8
5.8
0.02
10.0
11.4
0.64
25–35
79.5
84.1
75.7
77.1
35 and above
11.5
10.0
14.3
11.4
Education of mother
No or primary education
6.2
4.0
0.16
6.7
6.2
0.40
High school
10.7
9.4
13.8
11.0
Matriculate
12.2
10.9
10.0
15.7
Intermediate
32.8
33.7
31.0
26.7
Graduation
31.1
35.6
31.4
35.2
Higher
6.0
5.9
7.1
5.2
Occupation of mother
Home maker
90.9
90.2
0.63
89.5
93.8
0.11
Employee
9.1
9.8
10.5
6.2
Age of children
6–24 months
26.8
24.0
0.16
21.9
23.3
0.40
24–48 months
35.4
34.0
37.1
31.0
48–60 months
37.8
42.0
41.0
45.7
Sex of the child
Male
49.2
50.8
0.48
53.8
51.9
0.70
Female
50.9
49.1
46.2
48.1Immunization related information of the respondents under the two sampling schemes (Table4) shows that coverage of hepatitis B (at birth) vaccine is 58.4% and 55.8%, respectively, in 30 × 30 sampling scheme under cluster sampling and systematic sampling. On the other hand, it is 55.7% and 52.9% in 30 × 7 sampling scheme under two-stage cluster and systematic sampling, respectively.Table 4
Immunization related information of the respondents under the two sampling schemes (figures in %).
Sampling procedure
30 × 30
P value
30 × 7
P value
Variable
Cluster
Systematic
Cluster
Systematic
Hepatitis B at birth
Yes
58.4
55.8
0.27
55.7
52.9
0.56
No
41.6
44.2
44.3
47.1
Place of vaccination
Subdivisional civil hospital
22.2
22.3
0.46
19.5
23.3
0.25
Subcenters
18.2
20.9
22.9
20.5
Private hospitals
28.6
26.5
31.9
24.8
Private medical practitioner
31.1
30.3
25.7
31.4From the result, it is clear that people prefer private health sector as nearly about 60% prefer private health sector.Considering vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the two sampling schemes (Table5), it is observed that there is no significant difference between genders of children in both sampling schemes regarding their immunization of hepatitis B (at birth) vaccine. As the level of mother’s education increases, the percentage of vaccination (hepatitis B at birth) coverage also increases.Table 5
Vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the two sampling schemes (figures in %).
Sampling procedure
30 × 30
P value
30 × 7
P value
Background characteristics
Cluster
Systematic
Cluster
Systematic
Sex of child
Male
58.0
58.6
0.13
49.6
55.0
0.35
Female
58.7
52.5
62.9
50.5
Mother’s education
No or primary education
1.8
0
0.33
7.1
0
0.28
High school
20.0
12.9
24.1
13.0
Matriculate
27.5
23.5
19.0
24.2
Intermediate
63.4
54.1
64.6
60.7
Graduation
82.0
78.5
74.2
77.0
Higher
92.6
92.3
93.3
81.0
Religion
Hindu
59.8
57.6
0.01
54.9
55.6
0.72
Islam
41.0
24.2
54.5
28.6
Others
100.0
100.0
100.0
100.0
Caste
General
59.0
57.1
0.73
57.5
50.0
0.91
SC
56.1
53.8
44.7
59.4
ST
55.2
44.2
62.5
85.7
OBC
57.9
55.1
63.6
53.8
Monthly household income
Low
6.1
4.5
0.34
12.1
7.5
0.55
Middle
62.0
58.0
56.3
59.2
High
93.2
94.4
97.0
85.7Religion-wise, people belonging to others category (Christian, Jain) are 100% vaccinated whereas the remaining people are more or less 50% vaccinated against the vaccine (P=0.01 under 30 × 30 sampling scheme). There is no such difference of estimates of hepatitis B (at birth) vaccine coverage under the two methodologies considering the category of the study population. It is seen that children belonging to higher income families are more vaccinated (more than 90%) and coverage of hepatitis B (at birth) vaccine in lower income families is very low (4.5–12% only).Table6 representing place of vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the 30 × 30 sampling scheme shows that highly educated mothers prefer private health sector. Significant results are only in case of mother’s education (P=0.00), religion (P=0.01), and monthly household income (P=0.01) for subdivisional civil hospital under 30 × 30 sampling scheme.Table 6
Place of vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the 30 × 30 sampling scheme (figures in %).
Place of vaccination
Government health sector
Private health sector
Background characteristics
Subdivisional civil hospital
P value
Subcenters
P value
Private hospital
P value
Private medical practitioner
P value
Cluster
Systematic
Cluster
Systematic
Cluster
Systematic
Cluster
Systematic
Sex of child
Male
20.7
20.0
0.96
20.3
20.6
0.34
28.6
28.7
0.16
30.5
30.7
0.41
Female
23.8
24.9
15.9
21.3
28.7
24.0
31.7
29.8
Mother’s education
No or primary education
39.3
22.9
0.00
46.4
57.1
0.72
1.8
0
0.60
12.5
20.0
0.09
High school
41.1
32.9
38.9
50.6
10.5
5.9
9.5
10.6
Matriculate
36.7
23.5
34.9
52.0
9.2
14.3
19.3
10.2
Intermediate
21.0
30.0
15.3
16.5
23.7
22.4
40.0
31.0
Graduation
11.8
14.5
5.5
7.1
44.6
37.2
38.1
41.2
Higher
3.7
5.8
1.9
1.9
68.5
57.7
25.9
34.6
Religion
Hindu
20.9
22.2
0.01
18.6
19.9
0.41
29.4
27.5
0.06
31.0
30.3
0.16
Islam
35.0
27.3
17.0
37.9
18.0
9.1
30.0
25.8
Others
0
0
0
0
60.0
50.0
40.0
50.0
Caste
General
22.1
22.1
0.18
17.2
19.6
0.87
28.8
26.1
0.58
31.8
32.2
0.89
SC
22.3
18.9
21.6
28.0
26.6
25.9
29.5
27.3
ST
6.9
18.6
37.9
32.6
31.0
25.6
24.1
23.3
OBC
29.8
33.3
10.5
11.6
29.8
31.9
29.8
23.2
Monthly household income
Low
41.7
27.9
0.01
45.5
57.7
0.79
3.0
3.6
0.35
9.8
10.8
0.98
Middle
21.8
24.3
16.1
18.0
26.0
24.6
36.1
33.1
High
4.5
3.7
0.8
1.9
66.7
62.0
28.0
32.4Same result is seen in case of income of families as higher income families like to go to private health sector. Considering religion and caste of people, it is seen that more people prefer private health sectors. Compared with Table7 representing place of vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the 30 × 7 sampling scheme, it shows the same characteristics as Table 6.Table 7
Place of vaccination (hepatitis B at birth) of children by background characteristics of the respondents under the 30 × 7 sampling scheme (figures in %).
Place of vaccination
Government health sector
Private health sector
Background characteristics
Subdivisional civil hospital
P value
Subcenters
P value
Private hospital
P value
Private medical practitioner
P value
Cluster
Systematic
Cluster
Systematic
Cluster
Systematic
Cluster
Systematic
Sex of child
Male
18.6
21.1
0.69
30.1
21.1
0.09
28.3
24.8
0.65
23.0
33.0
0.49
Female
20.6
25.7
14.4
19.8
36.1
24.8
28.9
29.7
Mother’s education
No or primary education
21.4
23.1
0.96
50.0
46.2
0.41
7.1
0
0.11
21.4
30.8
0.78
High school
27.6
34.8
48.3
47.8
17.2
4.3
6.9
13.0
Matriculate
33.3
30.3
42.9
45.5
0
12.1
23.8
12.1
Intermediate
18.5
30.4
16.9
8.9
29.2
23.2
35.4
37.5
Graduation
15.2
12.2
10.6
8.1
45.5
37.8
28.8
41.9
Higher
6.7
18.2
0
0
80.0
54.5
13.3
27.3
Religion
Hindu
21.2
22.5
0.05
21.7
20.8
0.72
32.1
25.8
0.90
25.0
30.9
0.94
Islam
9.1
32.1
36.4
21.4
22.7
10.7
31.8
35.7
Others
0
0
0
0
75.0
75.0
25.0
25.0
Caste
General
17.6
24.7
0.20
22.9
20.9
0.95
34.6
21.5
0.39
24.8
32.9
0.59
SC
26.3
15.6
26.3
25.0
21.1
31.3
26.3
28.1
ST
12.5
0
25.0
14.3
37.5
42.9
25.0
42.9
OBC
27.3
35.8
9.1
7.7
27.3
38.5
36.4
15.4
Monthly household income
Low
24.2
27.5
0.24
51.5
52.5
0.22
9.1
5.0
0.50
15.2
15.0
0.99
Middle
22.9
24.6
21.5
14.8
26.4
24.6
29.2
35.9
High
0
10.7
0
3.6
78.8
53.6
21.2
32.1Calculating estimates of proportion of number of children undergoing hepatitis B vaccine, it is seen that ward number 11 has the highest coverage (93% in two-stage (30 × 30) cluster and 83% in systematic sampling). Ward number 2 shows the lowest coverage (17% in 30 × 30 cluster and 13% in systematic sampling).Values ofZ-statistic with confidence interval under 30 × 30 sampling scheme are given in Table 8. All Z-values are less than 1.96, except for ward number 37.Table 8
Estimates of proportion of number of children undergoing hepatitis B (at birth) vaccine and values ofZ-statistic with confidence interval under 30 × 30 sampling scheme.
Sl number
Ward number
Cluster (p1)
Systematic (p2)
|
Z
|-value
CI
1
2
0.17
0.13
0.36
(−0.15, 0.21)
2
4
0.70
0.67
0.28
(−0.20, 0.27)
3
5
0.25
0.47
1.89
(−0.48, 0.01)
4
11
0.93
0.83
1.19
(−0.06, 0.26)
5
12
0.53
0.57
0.26
(−0.29, 0.22)
6
15
0.60
0.60
0.00
(−0.25, 0.25)
7
17
0.47
0.43
0.26
(−0.22, 0.29)
8
18
0.70
0.70
0.00
(−0.23, 0.23)
9
24
0.17
0.27
0.96
(−0.31, 0.11)
10
25
0.67
0.47
1.58
(−0.05, 0.45)
11
26
0.63
0.67
0.27
(−0.28, 0.21)
12
33
0.73
0.80
0.62
(−0.28, 0.15)
13
35
0.40
0.53
1.05
(−0.38, 0.12)
14
36
0.63
0.57
0.53
(−0.18, 0.31)
15
37
0.63
0.37
2.07**
(0.03, 0.51)
16
38
0.43
0.50
0.52
(−0.19, 0.32)
17
40
0.53
0.37
1.30
(−0.42, 0.08)
18
42
0.73
0.63
0.84
(−0.13, 0.33)
19
43
0.67
0.50
1.32
(−0.08, 0.41)
20
46
0.53
0.53
0.00
(−0.25, 0.25)
21
47
0.57
0.53
0.26
(−0.22, 0.29)
22
48
0.60
0.53
0.53
(−0.18, 0.32)
23
50
0.80
0.73
0.62
(−0.15, 0.28)
24
51
0.63
0.67
0.27
(−0.28, 0.21)
25
53
0.67
0.63
0.09
(−0.23, 0.25)
26
54
0.63
0.50
1.05
(−0.12, 0.38)
27
55
0.37
0.53
1.30
(−0.42, 0.08)
28
57
0.70
0.67
0.28
(−0.20, 0.27)
29
59
0.57
0.63
0.53
(−0.31, 0.18)
30
60
0.83
0.67
1.49
(−0.05, 0.38)
31
Combine
0.58
0.56
0.85
(−0.03, 0.07)
**Significant at 5% probability level.Again, estimates of proportion of number of children undergoing hepatitis B vaccine in case of 30 × 7 sampling are given in Table9. It is seen that the highest coverage is 86% (ward number 11) and the lowest coverage is 0% in ward number 24. Values of Z-statistic with confidence interval under 30 × 7 sampling scheme show that except ward number 55 all other |Z|-values are less than 1.96.Table 9
Estimates of proportion of number of children undergoing hepatitis B (at birth) vaccine and values ofZ-statistic with confidence interval under 30 × 7 sampling scheme.
Sl number
Ward number
Cluster (p1)
Systematic (p2)
|
Z
|-value
CI
1
2
0.14
0.29
1.07
(−0.42, 0.12)
2
4
0.57
0.86
1.18
(−0.76, 0.19)
3
5
0.29
0.29
0.00
(−0.47, 0.47)
4
11
0.86
0.86
0.00
(−0.37, 0.37)
5
12
0.43
0.86
1.67
(−0.93, 0.07)
6
15
0.57
0.57
0.00
(−0.52, 0.52)
7
17
0.43
0.71
1.08
(−0.80, 0.23)
8
18
0.57
0.86
1.18
(−0.76, 0.19)
9
24
0.00
0.00
0.00
(0.00, 0.00)
10
25
0.71
0.29
1.60
(−0.10, 0.95)
11
26
0.57
0.57
0.00
(−0.52, 0.52)
12
33
0.86
0.86
0.00
(−0.37, 0.37)
13
35
0.71
0.43
1.11
(−0.22, 0.79)
14
36
0.71
0.71
0.00
(−0.47, 0.47)
15
37
0.71
0.43
1.08
(−0.23, 0.80)
16
38
0.57
0.43
0.53
(−0.38, 0.67)
17
40
0.71
0.43
1.08
(−0.23, 0.80)
18
42
0.86
0.57
1.18
(−0.19, 0.76)
19
43
0.57
0.43
0.53
(−0.38, 0.67)
20
46
0.57
0.57
0.00
(−0.52, 0.52)
21
47
0.57
0.14
1.67
(−0.07, 0.93)
22
48
0.71
0.43
1.08
(−0.23, 0.80)
23
50
0.57
0.57
0.00
(−0.52, 0.52)
24
51
0.43
0.71
1.08
(−0.80, 0.23)
25
53
0.43
0.71
1.08
(−0.80, 0.23)
26
54
0.43
0.57
0.53
(−0.67, 0.38)
27
55
0.43
0.14
2.09**
(0.02, 0.56)
28
57
0.71
0.86
0.65
(−0.57, 0.29)
29
59
0.57
0.57
0.00
(−0.52, 0.52)
30
60
0.86
0.86
0.00
(−0.37, 0.37)
31
Combine
0.56
0.53
0.11
(−0.49, 0.55)
**Significant at 5% probability level.Similarly, estimates of proportion of number of children undergoing hepatitis B vaccine (Table10) in case of 30 × 30 cluster and 30 × 7 cluster sampling show that there is no significant difference between these two methodologies.Table 10
Estimates of proportion of number of children undergoing hepatitis B (at birth) vaccine and values ofZ-statistic with confidence interval for larger and smaller cluster sampling.
Sl number
Ward number
30 × 30 (p1)
30 × 7 (p2)
|
Z
|-value
CI
1
2
0.17
0.14
0.15
(−0.27, 0.17)
2
4
0.70
0.57
0.65
(−0.27, 0.33)
3
5
0.23
0.29
0.29
(−0.42, 0.14)
4
11
0.93
0.86
0.66
(−0.20, 0.22)
5
12
0.53
0.43
0.50
(−0.30, 0.31)
6
15
0.60
0.57
0.14
(−0.38, 0.24)
7
17
0.47
0.43
0.18
(−0.37, 0.25)
8
18
0.70
0.57
0.65
(−0.27, 0.33)
9
24
0.17
0.00
1.16
(0.03, 0.23)
10
25
0.67
0.71
0.24
(−0.42, 0.14)
11
26
0.63
0.57
0.30
(−0.34, 0.27)
12
33
0.73
0.86
0.69
(−0.43, 0.03)
13
35
0.40
0.71
1.50
(−0.69, −0.12)
14
36
0.63
0.71
0.40
(−0.46, 0.11)
15
37
0.63
0.71
0.40
(−0.46, 0.11)
16
38
0.43
0.57
0.66
(−0.55, 0.07)
17
40
0.53
0.71
0.87
(−0.56, 0.01)
18
42
0.73
0.86
0.69
(−0.43, 0.03)
19
43
0.67
0.57
0.48
(−0.31, 0.30)
20
46
0.53
0.57
0.18
(−0.45, 0.17)
21
47
0.57
0.57
0.02
(−0.41, 0.20)
22
48
0.60
0.71
0.56
(−0.49, 0.08)
23
50
0.80
0.57
1.27
(−0.16, 0.43)
24
51
0.63
0.43
0.99
(−0.20, 0.41)
25
53
0.67
0.43
1.17
(−0.17, 0.44)
26
54
0.63
0.43
0.99
(−0.20, 0.41)
27
55
0.37
0.00
1.91
(0.19, 0.45)
28
57
0.70
0.71
0.07
(−0.39, 0.18)
29
59
0.57
0.57
0.02
(−0.41, 0.20)
30
60
0.83
0.86
0.15
(−0.32, 0.12)
31
Combine
0.58
0.56
0.12
(−0.38, 0.23)Comparison of larger systematic (30 × 30) and smaller systematic (30 × 7) sampling (Table11) also shows the same result (only ward number 35 has a significant value).Table 11
Estimates of proportion of number of children undergoing hepatitis B (at birth) vaccine and values ofZ-statistic with confidence interval for larger and smaller systematic sampling.
Sl number
Ward number
30 × 30 (p1)
30 × 7 (p2)
|
Z
|-value
CI
1
2
0.13
0.00
1.02
(0.01, 0.25)
2
4
0.67
0.86
0.99
(−0.50, 0.12)
3
5
0.47
0.29
0.87
(−0.20, 0.56)
4
11
0.83
0.86
0.15
(−0.32, 0.27)
5
12
0.57
0.86
1.43
(−0.60, 0.02)
6
15
0.60
0.57
0.14
(−0.38, 0.43)
7
17
0.43
0.71
1.34
(−0.66, 0.10)
8
18
0.70
0.86
0.84
(−0.46, 0.15)
9
24
0.27
0.00
1.54
(0.11, 0.42)
10
25
0.47
0.29
0.87
(−0.20, 0.56)
11
26
0.67
0.57
0.48
(−0.31, 0.50)
12
33
0.80
0.86
0.35
(−0.35, 0.24)
13
35
0.53
0.00
2.56**
(0.35, 0.71)
14
36
0.57
0.71
0.72
(−0.53, 0.23)
15
37
0.37
0.43
0.30
(−0.47, 0.34)
16
38
0.50
0.43
0.34
(−0.34, 0.48)
17
40
0.37
0.43
0.30
(−0.47, 0.34)
18
42
0.63
0.57
0.30
(−0.34, 0.47)
19
43
0.50
0.43
0.34
(−0.34, 0.48)
20
46
0.53
0.57
0.18
(−0.45, 0.37)
21
47
0.53
0.14
1.87
(0.08, 0.71)
22
48
0.53
0.43
0.50
(−0.30, 0.51)
23
50
0.73
0.57
0.84
(−0.24, 0.56)
24
51
0.67
0.71
0.24
(−0.42, 0.33)
25
53
0.63
0.71
0.40
(−0.46, 0.30)
26
54
0.50
0.57
0.34
(−0.48, 0.34)
27
55
0.53
0.14
1.87
(0.08, 0.71)
28
57
0.67
0.86
0.99
(−0.50, 0.12)
29
59
0.63
0.57
0.30
(−0.34, 0.47)
30
60
0.67
0.86
0.99
(−0.50, 0.12)
31
Combine
0.56
0.53
0.14
(−0.38, 0.44)
**Significant at 5% probability level.


## 5. Time and Cost Factor

To determine a better methodology, time and cost also play an important role. A comparison of time and cost factor between two-stage cluster and systematic sampling is given here. In case of 30 × 30 sampling scheme, it is seen that on average 148 households in each ward have been covered under cluster sampling and 459 households have been covered under systematic random sampling (Table12). As the figure shows that more household has been covered in systematic random sampling so also the time required for collecting the data is also higher and it is near about three times (on the basis of average figure) that the time spent in case of two stage cluster sampling.Table 12
Household covered in each ward under 30 × 30 and 30 × 7 sampling schemes.
Sl number
Ward number
Number of households covered
30 × 30
30 × 7
Cluster
Systematic
Cluster
Systematic
1
2
105
400
43
70
2
4
215
530
68
180
3
5
133
400
40
90
4
11
127
420
32
80
5
12
105
410
21
80
6
15
163
510
56
100
7
17
216
520
33
140
8
18
122
390
30
80
9
24
130
500
24
150
10
25
149
440
35
100
11
26
123
420
34
90
12
33
139
440
34
110
13
35
108
420
22
80
14
36
126
390
32
100
15
37
84
540
15
210
16
38
123
570
37
140
17
40
137
490
31
120
18
42
181
430
51
120
19
43
168
450
54
90
20
46
166
680
55
170
21
47
168
450
38
110
22
48
112
360
25
120
23
50
147
490
43
200
24
51
188
450
42
100
25
53
118
380
26
90
26
54
177
550
43
90
27
55
125
420
39
90
28
57
167
390
35
80
29
59
235
530
70
130
30
60
192
410
38
110
Total HH covered
4449
13780
1146
3420
Average HH covered
148
459
38
114As the time required is more, the cost incurred is definitely high in case of systematic sampling. Again, in case of 30 × 7 sampling scheme, the number of households covered (on average) in each ward is 38 (in two-stage cluster sampling) while, in case of systematic random sampling, it is 114 numbers which is three times more than that of the figure of the two-stage cluster sampling. It means that on average the required time is three times more in systematic sampling than in two-stage cluster sampling so cost incurred is higher in systematic sampling. Thus, we can say that, in both sampling schemes, systematic sampling is more time-consuming than the two-stage cluster sampling and hence the cost is higher in systematic random sampling in compared to that of two stage cluster sampling.


## 6. Conclusion

It is found that there is no significant difference between the estimates of hepatitis B (at birth) vaccine coverage under the three methodologies in demographic and health practices, family related information, and immunization related information of the respondents of the study population. Mother’s education plays an important role in case of vaccination coverage and selecting the place of vaccination. 30 × 7 sampling method failed to capture hepatitis B (at birth) vaccine coverage only in ward number 24. It is observed that both sampling schemes provide estimation of proportion of hepatitis B (at birth) vaccine coverage which is significantly not different at 5% level of probability indicating that it is insignificant and we have no evidence to reject the null hypothesis that there is no significant difference between the proportions of number of children undergoing hepatitis B (at birth) vaccine of two methodologies, namely, 30 × 30 cluster and systematic and 30 × 7 cluster and systematic sampling. On average, only 53–58% of children are vaccinated against hepatitis B. Coverage of hepatitis B (at birth) vaccine is moderate in this urban society of North-East India indicating poor child health scenario. It may be concluded that methodology-wise 30 × 7 sampling scheme (two-stage cluster sampling) will be preferred to 30 × 30 and systematic sampling because of quick estimation and lesser cost. But it is also to be noted that 30 × 30 sampling scheme will be more reliable than 30 × 7 sampling scheme as the sample size is larger in case of 30 × 30 sampling scheme than the later one.



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*Source: 850479-2014-08-07.xml*