Match List - I with List - II.

List - I

List - II

A. Regression threat

I. When participants drop out of a study systematically

B. Selection threat

II. When differences in groups are due to pre-existing conditions

C. Instrumentation threat

III. When changes in measurement tools affect the outcome

D. Confounding threat

IV. When an external variable influences the outcome

Choose the correct answer from the options given below

Question

List - I	List - II
A. Regression threat	I. When participants drop out of a study systematically
B. Selection threat	II. When differences in groups are due to pre-existing conditions
C. Instrumentation threat	III. When changes in measurement tools affect the outcome
D. Confounding threat	IV. When an external variable influences the outcome