Case control studies

Question 1

To what category of studies does case control belong to

Answer 1

observational studies

Question 2

what is a case control study

Answer 2

• one that is used to investigate possible causes of one disease.
• compares two groups of people ( cases and controls)
• cases are people with disease, control are ppl who don’t have the disease but may have other disease

Question 3

case controls can be analysed in what three ways

Answer 3

• if the factor of interest is continuous do a t-test on the case and control means
• if the factor is discontinuous, or can be grouped, calculate an odds ratio
• if the factor is discontinuous, or can be grouped, do a chi-squared test.

Question 4

how to calculate chi-squared for a table

Answer 4

• work out row and column totals
• calculate fraction of people in row and column totals
• calculate expected numbers in each cell (total x row fraction x column fraction)
• work out chi-squared statistic ( sum of (actual - expected)squared divided by expected

Question 5

how to calculate degrees of freedom

Answer 5

(number of rows - 1) x (number of columns -1)

Question 6

critical value is what

Answer 6

6.63