Evidence based healthcare special lecture I Final mini-test(Please see opposite side of the paper)
Department

Registration No.

18th July 2018, 18:30-20:00, D101

Name

1. Please specify the wrong points in explanation and/or method to analyze and suggest how to improve it(if no wrong point, answer so) for each issues underlined below.
(1) In R island with population size of about 4,000 in a developing country. When we see there with Google
Earth, almost equal-sized 40 villages are scattered. Recently the people with high fish and whale intake
are reported to suffer from neural damage symptoms. Due to the possibility of mercury poisoning, (A) 4villages were randomly selected from 40 villages, and in those 4 villages, all 400 residents were recruited tojoin the survey. They were interviewed about the frequency of fish/whale intake, such as [1] none or rarely,[2] monthly, [3] weekly, [4] daily, and the hair mercury concentrations of them were measured. The results(of which raw data are available from http://minato.sip21c.org/fish-Hg-2018.txt; variables are PID aspersonal ID number, HairHg as hair mercury concentration, HighHairHg is 1 if HairHg>=5, otherwise 0,and FishIL is one of 4 categories shown above) were summarized below.
Eating fish or whale

Nfrequency

MedianMean ± SD

High Hg（Hg µg/g hair）(Hg µg/g hair)≥5 µg/g hair

1. None80

3.44

3.55 ± 2.02

27

2. Monthly

90

4.34

4.72 ± 2.89

36

3. Weekly

120

5.45

5.36 ± 2.30

69

4. Daily110
5.97
6.20 ± 2.37
72
There are two approaches to analyze the relationships between fish/whale
intake and mercury exposure. First, the independence between High Hgand eating fish/whale frequency can be analyzed. (B) Fisher's exact test
resulted inand the null hypothesis was rejected, so thatthe relationship between the two variables is statistically significant.
Second, the effect of fish/whale intake on hair mercury concentration canbe analyzed. Welch's one-way ANOVA resulted in F-value of 24.273, firstd.f. of 3, second d.f. of 210.39, and p<0.001. (C) Then pairwise comparisonsof hair Hg levels between all pairs among 4 fish/whale intake frequencies
can be conducted by repeated use of Welch's t-test.

(A)
(B)
(C)

(2) Based on the result of large scale cohort study, brown rice intake is proved to significantly reduce thebody weight and white rice intake is proved to significantly increase the body weight. Then 5 obese patientschanged their stable food from white rice to brown rice. The changes of body weight (kg) between the 2timings (before intervention and after 6 months) were 70→65, 140→135, 95→85, 95→90, 85→80. The
result of paired t-test was p=0.0008, so that brown rice intake can be judged to have a significant weight
reduction effect as the result the intervention study.

(3) The gold standard method A can measure the concentration of biochemical marker for disease X, where
the concentration exceeds a specific threshold value. A cheaper and more rapid new method B wasdeveloped. Validity of B can be confirmed by showing the fact that the Pearson's correlation coefficient
between the measurements by A and B for the sufficient number of X patients and healthy volunteers ismore than 0.8 and that is statistically significant.

(4) The 44 chronic hepatitis patients were randomly divided into 2 groups. Treatment group was treated byprednisolone, the other (control group) was just observed. At the end of the study, 11 patients lived intreatment group, 6 lived in control group, but the result of Fisher's exact test was not significant (p=0.215).
The months until death or censoring (lived at the end of the study) were recorded in
http://minato.sip21c.org/hepatitis-2018.txt as time, with flag (1 if died, 0 if still lived) and group (1 fortreatment group, 2 for control group). For all patients (ignoring alive/dead), the mean survival months(109.5 months in treatment group and 64.7 months in control group) were compared by Welch's t-test, thenp=0.013, so that prednisolone has a significant effect of lengthen survival for chronic hepatitis patients.

2. Please explain the incidence rate of a disease. What type of study design is needed has to be included.

3. Sir Wright developed typhus vaccine and it was used in 6 studies conducted around 1900. In 1904, KarlPearson summarized the results by simply taking average of tetrachoric correlation coefficients of 6studies. The result was 0.193, which is judged as not enough strong to recommend as vaccine by KarlPearson. However, if we consider
the death as outcome, and conduct
the meta-analysis of odds ratios,
integrated odds ratio is 0.57
(95%CI, 0.48-0.67), which means
the vaccine having the significant
effect to reduce mortality. Please
explain why Pearson made awrong judge. Why we must nottake simple averages of correlation
coefficients?

4. Whether the ability of flash memory is improved by glucose candy or not was investigated for 10healthy volunteers. The result is shown below. Please test whether glucose candy improves flash
memory or not. P-value is needed. You can use computer software or calculator, but manual calculationis possible if you use 97.5% point of t-distribution with d.f. 9 is 2.262 and either of √2=1.414, √3=1.732,
or √5=2.236.
Scores before glucose candy

8637675876

Scores after glucose candy

97587969875. The RCT (Randomized Controlled Trial) to test new stretch method to improve body flexibility is to beconducted. Outcome measure is the change of standing-posture body anteflexion in centimeter. Basedon previous studies, the conventional stretch method increased 3 cm (standard deviation 2 cm) ofstanding posture body anteflexion measurement. If the new stretch method can increase more than4cm (as the difference from the conventional method, more than 1 cm) of standing posture body
anteflexion, it can be judged as clinically valuable. Please calculate needed sample size for this RCT for
2-tailed t-test with 5% significance level and 80% power, and assuming the same size of 2 groups.

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