Question

A random sample of 75 John Jay students reported that they studied 7 hours on average for their most difficult midterm exam. The standard deviation of the sample was 5 hours.  

a. Calculate the 95% Confidence Interval for the unknown parameter – the average time that John Jay students study for a difficult midterm exam.

Lower Bound

Upper Bound

Answer 1

df = n - 1 = 75 - 1 = 74

t critical value at 0.05 level at 0.05 level = 1.993

95% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

7 - 1.993 * 5 / sqrt(75) < < 7 + 1.993 * 5 / sqrt(75)

5.85 < < 8.15

95% CI is (5.85 , 8.15 )

Lower bound = 5.85

Upper bound = 8.15