Given the average outcomes for the treated and control groups, and their respective sample standard deviations, how does the number of observations impact the spread of a confidence interval?
A) Only increasing the number of treated will decrease the spread of the confidence interval
B) Only increasing the number of control groups will decrease the spread of the confidence interval
C) Only increasing the number of treated will increase the spread of the confidence interval
D) None of the answers is correct.

Question

Quizplus · Accepted Answer

The spread of a confidence interval is influenced by the sample size of both the treated and control groups, not just one or the other. Increasing the number of observations in either group generally decreases the spread of the confidence interval by reducing the standard error.

Given the Average Outcomes for the Treated and Control Groups