Arandom sample of 250 students at a university finds that these students take a mean of 15.3 credit hours per quarter with a standard deviation of 1.6 credit hours. estimate the mean credit hours taken by a student each quarter using a 95% confidence interval. round to the nearest thousandth.

OR

(15.102, 15.498)

Step-by-step explanation:

The formula to find the confidence interval is given by :-

, where n is the sample size

= sample standard deviation.

= Sample mean

= Two tailed z-value for significance level of .

Given : Confidence level = 95% = 0.95

Significance level =

sample size : n= 250 , which is extremely large ( than n=30) .

So we assume sample standard deviation is the population standard deviation.

thus ,

By standard normal  distribution table ,

Two tailed z-value for Significance level of 0.05 :

Then, the 95% confidence interval for the mean credit hours taken by a student each quarter :-

Hence, the mean credit hours taken by a student each quarter using a 95% confidence interval. =(15.102, 15.498)

78.59 is the mean

step-by-step explanation: