A group of statistics students decided to conduct a survey at their university to find the average (mean)amount of time students spent studying per week. Assuming a population standard deviation of three hours,what is the required sample size if the error should be less than a half hour with a 99% level of confidence?
A)196
B)239
C)15
D)16

Question

Quizplus · Accepted Answer

The formula to calculate the required sample size is:

n = (Z*σ/E)^2

Where,

Z = Z-score for the desired level of confidence (99% = 2.58) 
σ = Population standard deviation (given as 3 hours) 
E = Margin of error (0.5 hours)

Plugging in the values, we get:

n = (2.58*3/0.5)^2 = 239.13

Rounding up to the nearest whole number, the required sample size is 239.

A Group of Statistics Students Decided to Conduct a Survey