Question

1a) A survey was conducted to estimate the prevalence of a disease among a student population. What type of epidemiological study is this?

Case-control

Cluster randomized trial

Longitudinal

Cross-sectional

Cohort

1b) Would this type of study be affected by selection bias? How?

1c) Would such bias affect prevalence estimate? How?

Answer 1

1a) A survey was conducted to estimate the prevalence of a disease among a student population. What type of epidemiological study is this?

The correct answer is

(5)Cross sectional study

In a cross sectional study, we collect information about a health state at a single point in time, with the help of a survey, This data allows you to count the number of existing study units meeting the above definition, which is the prevalence of a disease among a student population.

1b) Cross sectional study design is also affected by selection bias, it occurs when the study participants are systematically different in their characteristics compared with the eligible participants who were not selected for the study, thus when the exposed and unexposed groups have differences in important outcome predictors, the results may be selection biased.

If the selection of students was restricted to a group with higher or lower susceptibility of diseases, selection bias occurs.

1c) Consequently, selection bias affects the estimate of prevalence, as we have the same number of students, but if the investigators used selection procedures that were somewhat more likely to select students who had the exposure of disease, As a result, the estimate of effect, the odds ratio, will be biased.