Question

A team of cognitive psychologists studied the effects of sleep deprivation on decay of short-term memory. Eight participants stayed in a lab for 2 days. Four were randomly assigned not to sleep during that period. The other four were allowed to sleep when they wanted to do so. At the end of the 2 days, the participants completed a short-term memory task. Here are the results:

Mean Time (Seconds) for Remembering

Sleep Deprived	Normal Sleep
7	9
8	8
7	11
9	7

Based on these results, does sleep deprivation reduce short-term memory?
(Use the .05 significance level.)

1. Use the five steps of hypothesis testing.
2. Figure the effect size.   

Answer 1

Solution:

Sleep Deprived

Number of samples = 4

Mean = 7.75

Standard deviation = 0.9574

Normal Sleep

Number of samples = 4

Mean = 8.75

Standard deviation = 1.7078

Effect size
The observed standardized effect size is large (0.72). That indicates that the magnitude of the difference between the average and average is large.