Test 33 (Statistics and epidermiology) 
1. A normal population distribution is needed for the following statistical 
a. chi-squared

b. variance estimation

c. standard error of the mean

d. Student's t-test

e. Kendall's rank coefficient.

2. With regard to statistics:
a. the mode is the most frequently occurring value

b. the mode is the maximum point on a frequency distribution 

c. the median has an equal number of values above and below 

d. in a normal distribution the mean, mode and median coincide

e. about 95% of observations lie within two standard 
     deviations of the mean

3. With regard to the chi-squared test:

a. it is used to test the difference between frequencies

b. it is used as an alternative to the t-test to determine the 
    difference between two means

c. the number of degrees of freedom is the number of 
    independent comparisons.

d. the greater the value of the chi-squared test, the less likely it 
     is to be significant

e. the null hypothesis is not required.


4. The prevalence rate of a disease has the following features:
a. it is dependent on the incidence of the disease

b. it is dependent on the duration of illness

c. it measures all the current cases in the community

d. it can be estimated from a cross-sectional study

e. it can be used to determine the health needs of a community

5. An aetiological factor must satisfy the following before one can say that it 
    is causally related to a disease:

a. exposure to the factor must precede the development of the 

b. elimination of the factor decreases the risk of the disease

c. the factor is found more frequently among the diseased than 

d. the factor is not found among persons without the disease

e. the factor is found in all cases with the disease

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