Answer:
100 students should be surveyed in order to cut the width of the interval down from 3 hours to 1.5 hours
Step-by-step explanation:
Given that a 95% confidence interval, based upon a sample of size 25, for the mean number of hours of sleep that college students get per night was 5 to 8 hours.
Confidence interval = (5,8)
This implies that mean = 6.5 and margin of error = 1.5
i.e.
If the interval width to be cut into half then the
New confidence interval = (5.75, 7.25)
Margin of error = 0.75
This is possible only when new n= 100
Hence sample size should be increased to 100
100 students should be surveyed in order to cut the width of the interval down from 3 hours to 1.5 hours