An analyst takes a random sample of 25 firms in the telecommunications industry and constructs a confidence interval for the mean return for the prior year. Holding all else constant, if he increased the sample size to 30 firms, how are the standard error of the mean and the width of the confidence interval affected? 
Definitions:
Test-Retest Reliability
The consistency of a measure or test over time when administered to the same individuals on two occasions.
Test-Retest Correlation
A measure of the consistency of a psychological test or assessment over time by administering the same test to the same individuals on two different occasions.
Median
The score that falls in the middle of all the scores on the test; also called the 50th percentile.
Predictive Validity
When a scale is related to a concrete outcome or behavior.
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