--------

) 

Headache as the Reason for Office Visits, National 

Ambulatory Medical Care Survey: United States, 1977-78 

p~t)l%?W flF l’?l~ ,­ ‘ .. =.=. by Beulah K. Cypress, Ph.D., Division of Health Care Statistics PUBLICANINS MAMX 

Headache was the principal cause of an estimated 

18,341,923 visits to office-based physicians during 

1977-78. Headache was the seventh most frequent 

symptomatic reason for visits given by patients. 

The estimates in this report are based on data 

collected in the National Ambulatory Medical Care 

Survey (NAMCS), a probability sample survey conducted yearly by the Division of Health Care Statistics 

of the National Center for Health Statistics. Since the 

estimates presented in this report are based on a 

sample rather than on the entire universe of officeQed physicians, the data are subject to sampling 

ability. The Technical Notes at the end of this 

* ,ort provide a brief explanation of sampling errors 

and guidelines for judging the precision of the estimates 

presented. A more detailed description of the sample 

design and additional definitions of certain terms used 

in NAMCS have been published elsewhere. 1 

Figure 1 is a facsimile of the 1977-78 Patient 

Record used by participating physicians to record 

information about office visits. The patient’s complaint, symptom, or other reason for the visit, expressed 

as nearly as possible in the patient’s own words, is 

recorded by the physician in item 6. The principal 

reason (listed. fkst ti this item) is the one that in 

the physician’; judgment was most responsible for the 

patient making the visit. Data on principal reason were 

classified and coded according to a reason for visit 

classification system presented in another report.z 

Since 1977 was the first year that this classification 

system was used, caution should be exercised in comparing data presented in this report with those of prior 

years. 

1National Center for Health Statistics: The National Ambulatory Medical 

Care Survey, 1977 summary: United States, January-December 1977, by 

T. Ezzati and T. McLemore. Vital and Health Statistics. Series 13-No. 44. 

DHEW Pub. No. (PHS) 80-1795. Public Health Service. Washington. U.S. 

overnment Printing Office, Apr. 1980. 

.ional Center for Health Statistics: A reason for visit classification for 

;latory care, by D. Schneider, L. Appleton, and T. McLemore. Vital 

Health Statistics. Series 2-No. 78. DHEW Pub. No. (PHS) 79-1352. * 

ti.~. Government Printing Office, Feb. 1979. 

Data highlights EDITORIALLM?ARY 

Table 1 provides the age and sex of patients who 

visited office-based physicians for medical care related 

to headache. The average annual rate of these visits 

increased with the advancing age group of the patients. 

Females over 15 years of age tended to visit more 

frequently for headache problems than males did. Visit 

rates for female patients over 44 year8 of age were 

about twice as high as those for their male counterparts. 

Headache accounted for about the same proportion 

of total visits regardless of the geographic location of 

Table 1. Number, percent distribution, and average annual rate of office 

visits with headache as the principal reason for visit by sex and age of 

patient: United States, 1977-78 

Average 

Number of annual 

Percent Sex and age visits in visit rate distribution thousands per ?,000 

Both sexes 

Alleges . . . . . . . . . . . . . 18,342 100.0 43.2 

Under 15years . . . . . . . . 1,793 9.8 17.6 

15-24 years . . . . . . . . . . 2,486 13.6 31.4 

254years . . . . . . . . . . 5,996 32.7 53.8 

45-64 years . . . . . . . . . . 5,196 28.3 60.2 

65 years and over . . . . . . . 2,871 15.7 63.9 

Female 

All ages . . . . . . . . . . . . . 12,148 66.2 55.4 

Under 15years . . . . . . . . 787 4.3 15.8 

15-24 years . . . . . . . . . . 1,645 9.0 40.8 

25-44 years . . . . . . . . . . 3,858 21.0 67.0 

45-64 years . . . . . . . . . . 3,699 20.2 82.0 

65 years and over. . . . . . . 2,159 11.8 81.8 

Male “ 

Alleges . . . . . . . . . . . . . 6,194 33.8 30.3 

Under 15years . . . . . . . . 1,006 5.5 19.4 

15-24 years . . . . . . . . . . 841 4.6 21.7 

25-44 years . . . . . . . . . . 2,138 11.7 39.7 

45-64 years . . . . . . . . . . 1,496 8.2 36.3 

65 years and over . . . . . . . 713 3.9 38.4 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, Public Health Service, Office of Health Research, Statistics, and Technology 
---

‘“’ES

2 akmcedm . , 

Symbols 0’ 

‘, 

Data not available ,, 

‘1 . . . Category not applicable 

Quantity zero 1 

0.0 Quantity more than O but lessthan 0.05 I 

* Figure does not meet standards of i 

reliability or precision 

(

Figure 1. NATIONAL AMBULATORY MEDICAL CARE SURVEY PATl ENT RECORD FORM: 

1977-78 

ASSURANCE OF CO NFIDENTIALITY-AII Infwmmion which would permit Identification of m Individual,


. practice.or m establishmentwill be held confidential,will be usedonly by persms engagedIn and for


the Purposes of the survey .“d will nor be disclosedw releasedto c.zherDersomor usedfor .“” .mherp.rpos. 

A 033012


1. DATE OF VISIT PATlENT RECORD 

NATIONAL AMBULATORY MEDICAL CARE SURVEY 

xiJt2. DATE OF BIRTH 3. SEX 4. COLOR OR !i WAS PATIENT 6. PATlENT’S COMPMINTIS), SYMPTOM(S), OR OTHER If RACE REFERRED FOR REASON(S) FOR THIS VISIT 

THIS VISIT BY (In patient’s own words) 

, � WHITE ANOTHER 

I � FEMALE 2 � NEGROI PHYSICIAN? a MOST G7&7&- BLACK IMPORTANT ): 2 � MALE 1 � YES 3 � OTHER b. OTHER 

* � UNKNOWN 20N0 

7.	 TIME SINCE ONSET 8. PHYSICIANS DIAGNOSES 9. HAVE YOU SEEN 10. SERIOUSNESS OF 

OF COMPLAINTI PATIENT BEFORE? CONDITIO#J IN 

SYMPTOM IN ITEM 6s ., PRINCIPAL DIAGNOSISm ROBLEM A530ciATED WITH ITEM & (Check one) 

(Check one) ITEM 6a I � YES ,ONO 

+ I � VERY SERIOUS ( 

I � LESS THAN 1 DAY IF YES, FOR TI+E 2 � SERIOUS 

, � 1-6 DAYS CONDITION IN 

b. OTHER SIGNIFICANT CURRENT DIAGNOSES ITEM 0.? SLIGHTLY 30 , � 1-3wEEKS SERIOUS 

11. 

::%:~:..: 

DIAGNOSTIC SERVICES 

-

THIS 

~ 

12. THERAPEUTIC SERVICES THIS 13. DISPOSITION THIS VISIT 

‘n””4oNoTs

14. DURATION OF 

VISIT (Check all ordsmd or provided) VISIT (Chsck all ordersd or provided) (Check all thar app/y) THIS VISIT 

, � NONE , � NONE (Time sctually 

, � LIMITED ExAM/HISTORY 2 � iMMUNIZATION/ : � NO FOLLOW-UP PLANNEO spent m“th 

z � GENERAL EXAMIHISTORY DESENSITIZATION a � RETURN AT SPECIFIED TIME physician] 

4 � PAP TEST 3 � DRUGS (P RESCRIPTIONI 1 � RETURN IF NE EDEO, P.R.N. 

NONPRESCRIPTION) 

> � CLINICAL LAB TEST 4 � TELEPHONE FOLLOW-UP PLANNEO ~ � DIET COUNSELING 

6 � X. RAY $ � FAMILY PLANNING 5 � REFERRED TO OTHER PHYSICIAN _ MINUTES , ~ EKG 6 � MEDICAL COUNSELING 

, � VISION TEST 7 � PHYSIOTHERAPY 6 � ‘ETURNEDTO REFERRING PHYSICIAN 

, � EN DOSCOPY D � OFFICE SURGERY 7 � ADMIT TO HOSPITAL 

,. � BLDOD PRESSURE CHECK * � PSYCH OTHERAPYI 

I i � OTHER (Specify) THERAPEUTIC LISTENING ‘ � OTHER (Specify) 

, 0 � OTHER (Specify) 

I HRA-34-2 DEPARTMENT OF HEALTH, EOUCATION AND WELFARE O.M. B. =68-R1498 

REV. 9-76 PUS LICHEALr HSEHVICE 

HEALTH RESOURCES ADMINISTRATION / 

NATl ONAL CENTER FOR HEALTH StatiStiCS 

/( b, 

I 
denceMa3 

Table 2. Number of office visits and number, percent, and average annual 

rate of office visits with headache as the pfi ncipal reason for visit, by 

location of physician’s practice: United States, 1977-78 

Number in thousands Averegs 

annual 

Location of practice All visits Visits for Percent visit rate 

headache per 1,000 

persons 

Geographic region 

Northaast . . . . . . . . . . . 271,440 4,580 1.7 47.1 

North Central . . . . . . . . . 291,571 4,404 1.5 38.6 

south . . . . . . . . . . . . . . 355,754 5,613 1.6 40.6 

Wast . . . . . . . . . . . . . . 235,785 3,745 1.6 50.5 

,Type of area 

Metropolitan. . . . . . . . . . 865.549 13.479 1.6 46.5 

metropolitan . . . . . . . 289;001 4;863 1.7 36.3 

the physician’s practice (table 2). However, visit rates 

varied, indicating higher utilization rates in the Northeast and West Regions than in the North Central and 

South, and in metropolitan than in nonmetropolitan 

areas. 

The specialists most commonly visited by patients 

presentkg headache as the reason for visit are shown 

in table 3. Eighteen percent of visits to neurologists 

were made by patients with a principal complaint of 

headache. Other specialists treated headache patients 

in 1 or 2 percent of their visits. 

Table 3. Number of office visits and number and percent of office visits 

with headache as the principal reason for visit, by selected physician 

specialties: United States, 1977-78 

Number in thousands 

Visits for ‘ereent All visits headache 

e 

Allspecialties . . . . . . . . . . . . . . . 1,154,550 18,342 1.6 

eral and family practice . . . . . . . 433,936 9,528 2.2 

al medicine . . . . . . . . . . . . . 133,291 2,754 2.1 

ribs . . . . . . . . . . . . . . . . . . 114,921 905 0.8 

ral surgery . . . . . . . . . . . . . . 69,223 584 0.8 

Ophthalmology . . . . . . . . . . . . . . 58,851 1,053 1.8 

Neurology . . . . . . . . . . . . . . . . . 5,108 938 18.4 

Otolaryngology . . . . . . . . . . . . . . 32,193 802 2.5 

Patients who developed a headache that was a 

new problem were likely to visit their physicians 

within 3 weeks of its onset, with over 40 percent of 

visits occurring in less than a week (table 4). 

About half the visits for headache involved a condition evaluated by the physician as not serious in nature 

(table 5). There was no statistically significant difference in this proportion by sex of the patient. 

The principal diagnosis made by the physician for 

the patient who presents headache as the chief complaint is recorded in item 8 of the Patient Record. 

Diagnostic codes are based on the Eighth Revision 

International Classification of Diseases (ICDA).3 Table 

6 contains a list of the diagnoses most frequently 

associated with headache. Headache, as a diagnosis, 

appeared in an estimated 31 percent of such visits 

(ICDA codes 306, 346, and 791). An additional 14 

percent were attributed to hypertension. 

3Nation~ Center for Health Statistics: Eighth Revision Interna*”onal 

Classification of Diseases, Adapted for Use in the United States. H-E Pub. 

No. 1693. Public Health Service. Washington. U.S. Government Printing 

Office, 1967. 

Table 4. Percent of office visits with headache as a new problem, by sex 

of patient and time since onset of complaint: United States, 1977-78 

Time since onset of complaint Female Male 

. Percent 

Lessthan l week . . . . . . . . . . . . . . . . . . . 43.9 49.3 

l-3weeks . . . . . . . . . . . . . . . . . . . . . . . 16.3 22.7 

l-3 months . . . . . . . . . . . . . . . . . . . . . . . 16.1 13.6 

Morethan3 months . . . . . . . . . . . . . . . . . 20.5 13.7 

Table 5. Percent distribution of office visits with headache as the principal reason for visit, by seriousness of problem, according to sex of 

patient: United States, 1977-78 

Seriousness of problem Female Male 

Percent distribution 

All visits . . . . . . . . . . . . . . . . . . . . . . . . . 100.0 100.0 

Notserious . . . . . . . . . . . . . . . . . . . . . . . . 51.4 47.3 

Slightly serious . . . . . . . . . . . . . . . . . . . . . 35.6 38.3 

Serious orvery serious . . . . . . . . . . . . . . . . . 12.9 14.5 
� 

4 adwncedata 

Table 6. Number and percent distribution of office visits with headache Table 8. Percent distribution of office visits with headache astheprincias the principal reason for visit by principal diagnosis: United States, pal reason forvisit byduretion anddisposition ofvisiti United States, 

1977-78 1977-78 

Principal diegnosis and ICDA code ~ 

Number of 

visits in 

Percent 

distribution Duretion anddisposition 

Percent 

distribution 

thousands of visits 

All diagnoses . . . . . . . . . . . . . . . . . . . 18,342 100.0 All Visits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100.0 

Neuroses . . . . . . . . . . . . . . . . ..3oo 653 3.6 Duration 

Special symptoms not elsewhere 

classified . . . . . . . . . . . . . ...306 1,692 9.2 Ominutasl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 

Migraine . . . . . . . . . . . . . . . . . .346 

Refractive errors . . . . . . . . . . . . . 370 

1,635 

500 

8.9 

2.7 

I-sminutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

6-10 minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

11.2 

26.9 

Essent~al benign hypertension. . . . . . 401 2,494 13.6 11-15minutes. .c . . . . . . . . . . . . . . . . . . . . . . . . 30.5 

Acute upper respiratory infection of 

multiple or unspecified sites . . . . . . 465 640 3.5 

16-30minutes . . . . . . . . . . . . . . . . . . . . . . . . . . . 

31 minutes ormore . . . . . . . . . . . . . . . . . . . . . . . . 

21.7 

7.5 

Chronic sinusitis. . . . . . . . . . . . . . 503 1,332 7.3 Disposition 

Hay fever . . . . . . . . . . . . . . . . .. 507 

Haadache3 . . . . . . . . . . . . . . . . . 791 

Concussion . . . . . . . . . . . . . . . ..850 

All other diagnoses . . . . . . . . . . residual 

420 

2,303 

345 

6,328 

2.3 

12.6 

1.9 

34.5 

No followup planned . . . . . . . . . . . . . . . . . . . . . . . 

Return atspecified time.... . . . . . . . . . . . . . . . . . 

Return ifneeded, p.r.n . . . . . . . . . . . . . . . . . . . . . . 

Telephonefollowupplanned . . . . . . . . . . . . . . . . . . 

9.4 

52.4 

32 

1 Based on the E jghth Revision International 

Adapted for Use in the United States ( ICDA). 

Classification Of Disease, Referred to otherphysician. . . . . . . . . . . . . . . . . . . 

Return to referring physician . . . . . . . . . . . . . . . . . . 

4. 

9*1.8 

2The~a racOrds cOded 306.8, the ICDA category for cephalalgia, in- Admitto hospital . . . . . . . . . . . . . . . . . . . . . . . . . *1.2 

cluding headache of nonorganic origin and tension headache. Otherdisposition . . . . . . . . . . . . . . . . . . . . . . . . . *0.8 

3Excludes heedache of nonorganic origin (306.8), migraine (346), and Ivisits jn which there was no face-to-face contact betwaen the patient 

tension haadache (306.8). and the physician. 

2Wi]l not total 100. Osince more than one disposition was possible. 

Table 7. Percent of office visits with headache as the principal reason for 

visit, by selected diagnostic and therapeutic sewicas ordered or provided: United States, 1977-78 

Percent 

Diagnostic and therapeutic services of visits The potential presence ofhypertensionis reflected 

in the higher than average proportion ofvisits in which 

Diagnostic services blood pressure was measured. Table 7 shows that 

None . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 

Limited exam/history . . . . . . . . . . . . . . . . . . . . . . 62.2 blood pressure was checked during4 9percent ofvisits


General exam/history . . . . . . . . . . . . . . . . . . . . . . . 23.9 for headache compared with the NAMCS average of


Pap test...............<.. . . . . . . . . . . . . . *1.4 34percent ofall visits.


Clinical lab test . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2


X-ray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.0 Drug therapy (either prescription ornonprescrip-


EKG, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 tion) was used in 74 percent of visits, a proportiontithat


Vision test, . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 exceeded the average of53 percent of all NAMCS visits.


8100d pressurecheck . . . . . . . . . . . . . . . . . . . . . . . 49.2


Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Table 7 also shows the percent of visits in which


Therapeutic services various diagnostic and therapeutic services were either 

ordered or provided. None . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2


lmmunization/dasensitization. . . . . . . . . . . . . . . . . . 3.1 Table 8 provides data on the duration and dis-


Drugs (prescription/nonprescription). . . . . . . . . . . . . . 73.8 position of visits for headache.


Dietcounseling . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Additional data on headache andother reasons for


Medical counseling . . . . . . . . . . . . . . . . . . . . . . . . 21.0


Physiotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.0 visits will be presented in more detail inareportf


Officesurgery . . . . . . . . . . . . . . . . . . . . . . . . . . . *1.3 the Vital and Health. Statistics series. Quest


Psychotherapy /therapeutic listening . . . . . . . . . . . . . . 5.0 regarding this report may be directed to the Ambu
 9 

Other . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,6 

tory Care Statistics Branch by calling301 -436-7132. 
5


@ 

@ 

Technical notes 

Source of data 

The information presented in this report is based on 

data collected in the National Ambulatory Medical 

Care Survey (NAMCS) during 1977 and 1978. Tine 

NAMCS universe is composed of office visits made 

within the conterminous United States by ambulatory 

patients to nonfederally employed physicians who are 

principally engaged in office practice and are not in 

the specialties of anesthesiology, pathology, or radiology. The National Opinion Research Center, under 

tract to the National Center for Health Statistics, 

sponsible for the NAMCS field operations. 

Sample design 

NAMCS utilizes a multistage probability design that 

involves samples of primary sampling units (PSU’s), 

physician practices within PSU’S, and patient visits 

within physician practices. For 1977-78 a sample of 

6,007 non-Federal, office-based physicians was selected 

from master fdes maintained by the American Medical 

Association and the kmerican Osteopathic Association. 

The physician response rate for this period was 75.1 

percent. Sampled physicians were requested to complete Patient Records (figure 1) for a systematic random 

sample of office visits taking place during a randomly 

assigned weekly reporting period. During 1977-78, 

98,335 Patient Records were completed by responding 

physicians. 

Sampling errors 

The standard en-or is primarily a measure of the 

sampling variability that occurs by chance because 

only a sample, rather than the entire universe, is 

sampled. The relative standard error of an estimate is 

obtained by dividing the standard error of the estimate 

the estimate itself and is expressed as a percent of 

estimate. Relative standard errors for aggregate 

atistics are shown in tables I and H. Standard errors 

for estimated percentages are shown in tables III and 

IV. 

Table 1. Approximate relative standard errors of estimated numbers 

of office visits based on all physician specialties: NAMCS, 1977-78 

Relative 

Estimated number of office standard 

visits in thousands error in 

percent 

500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.9 

1,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 

2,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.7 

5,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 8.3 

10,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 

20,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 

50,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 

200,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 

1,000,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 

Example of use of table: An aggregate of 15,000,000 visits has a relative 

standard error of 5.5 percent, or a standard error of 825,000 visits (5.5 

percent of 1 5,000,000). 

Table II. Approximate relative standard errors of estimated numbers 

of office visits based on an individual physician specialty: NAMCS, 

1977-78 

Relative 

Estimated number of otice standard 

visits in drousands error in 

percent 

500 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.0 

1,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 

2,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5 

5,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 

10,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 

20,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 

50,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 

100,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 

400,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 

Example of use of table: An aggregate of 7,500,000 visits has a relative 

standard error of 9.4 percent, or a standard error of 705,000 visits (9.4 

percent of 7,500,000). 

Definitions 

Ambulatory patient. –An ambulatory patient is an 

individual presenting himself for personal health 

services who is neither bedridden nor currently admitted to any health care institution on the premises. 
6 

O.ffice.-An office is a place that the physician 

identifies as a location for his ambulatory practice. 

Responsibility over time for patient care and professional services rendered there generally resides with the 

individual physician rather than an institution. 

Visit.–A visit is a direct personal exchange between 

an ambulatory patient and a physician, or between a 

patient and a staff member working under the physician’s supetiision, for the purpose of seeking care and 

rendering health services. 

P/zyskian.–A physician is a duly licensed doctor 

of medicine (M.D.) or doctor of osteopathy (D.O.) 

currently in office-based practice who spends time in 

caring for ambulato~ patients. Excluded from NAMCS 

are physicians who are hospital based; physicians who 

specialize in anesthesiology, pathology, or radiology; 

physicians who are federally employed; physicians who 

treat only institutionalized patients; physicians employed full time by an institution; and physicians who 

spend no time seeing ambulatory patients. 

Table II 1. Approximate standard errors of percents of estimated numbers 

of office visits based on all physician specialties: NAMCS, 1977-78 

Table IV. Approximate standard errors of percents of estimated numbers 

of office visits based on an individual physician specialty: NAMCS, 

1977-78 

Base of percent 

Estimaiad percent 

(number of office Ior 5or 10or 200r 300r Go visits in thousands) 99 95 go 80 70 

Standard error in percentage points 

500 . . . . . . . . . . ...2.6 5,7 7.9 10.5 12.1 13.1 

1,000. . . . . . . . . . . . 1.9 4.1 5.6 7.4 8.5 9.3 

2,000. . . . . . . . . . . . 1.3 2.9 3.9 5.3 6.o 6,6 

5,000. . . . . . . . . . . . 0.8 1.8 2.5 3.3 3.8 4.2 

10,000. . . . . . . . . . . 0.6 1.3 1.8 2.4 2.7 2.9 

20,000. . . . . . . . . . . 0.4 0.9 1.2 1.7 1.9 2.1 

50,000. . . . . . . . . . . 0.3 0.6 0.8 1.1 1.2 1.3 

100,000 . . . . . . . . . . 0.2 0.4 0.6 0.7 0.9 0.9 

400,000 . . . . . . . . . . 0.1 0.2 0.3 0.4 0.4 0 

Example of use of table: An estimate of 90 percent based on an aggre 

Of 3,500,000 visits has a standard error of 3.2 per=ant,or ~ reIa standard error of 3.6 percent (3.2 percant + 90 percent). 

Base of percent 

(number of office 

visits in thousands) 

500 . . . . . . . . . . ...2.5 

1,000. . . . . . . . . . . . 

2,000 . . . . . . . . . . . . 

5,000. . . . . . . . . . . . 

10,000 . . . . . . . . . . . 

20,000 . . . . . . . . . . . 

50,000 . . . . . . . . . . . 200,000 . . . . . . . . . . 

1,000,000. . . . . . . . . 

Estimated percent 

Ior 5or 10 or 20 or 30 or so 99 95 go 80 70 

Standard error in percentage points 

5.4 7.4 9.9 11.4 12.4 

1.7 3.8 5.3 7.0 8.0 8.8 

1.2 2.7 3.7 !3.0 5.7 6.2 

0.8 1.7 2.3 3.1 3.6 3.9 

0.6 1.2 1.7 2.2 2.5 2.8 

0.4 0.9 1.2 1.6 1.8 2.0 

0.2 0.5 0.7 1.0 1.2 

0.1 0.3 0.4 0.5 ;:; 0.6 

0.1 0.1 0.2 0.2 0.3 0.3 

Example of use of table: An estimata of 20 percent based on an aggregate 

of 15,000,000 visits has a standard error of 1.9 percent, or a relative 

stendard error of 9.5 percent ( 1.9 parcent + 20 percent). 
7


Recent Issues of Advance Data From Vital and Health Statistics 

No. 66. Visits to Family Planning Sites: United States, 1977 

(In preparation) 

No. 65. Cough as the Reason for Office Visits, National AmbuIatory Medical Care Survey: United States, 1977-78 (Issued: 

November 5, 1980) 

No. 64. Health Practices Among Adults: United States, 1977 

(Issued: November 4, 1980) 

No. 63. Office Visits for Male Genitourinary Conditions: National Ambulatow Medical Care Survey: United States, 1977-78 

(ksued: November 3, 1980) 

No. 62. Expected Principal Source of Payment for Hospital Discharges: United States, 1977 (Issued: October 31, 1980) 

A complete list of Advance Data From Vital and Health Statitr”cs is available from the Scientific ~d Technical Information Branch.