Question

2. A sample of ACT scores for 20 students in Basic Math revealed a mean score of 10 with a standard deviation of 3. Find a 96 percent confidence interval for the mean ACT score for all basic math students.

Answer 1

Given that,

= 10

s =3

n = 20

Degrees of freedom = df = n - 1 = 20- 1 =19

At 96% confidence level the t is ,

t /2,df = t0.02,19 =2.205 ( using student t table)

Margin of error = E = t/2,df * (s /n)

= 2.205* ( 3/ 20) = 1.4792

The 96% confidence interval estimate of the population mean is,

- E < < + E

10 -1.4792 < <10 + 1.4792

8.5208 < < 11.4792

( 8.5208 , 11.4792)