In: Math
A school administrator is interested in a schools performance in math. He administers a math test to a sample of 30 students and obtains a mean of 84.25. The standard deviation of this sample was 8.4. (T Test)
26. Construct a 95% confidence interval for this data.
27. How would you interpret this confidence interval?
olution :
Given that,
= 84.25
s =8.4
n =30
Degrees of freedom = df = n - 1 = 30- 1 = 29
a ) At 95% confidence level the t is ,
= 1 - 95% = 1 - 0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
t /2,df = t0.025,29 = 2.045
Margin of error = E = t/2,df * (s /n)
= 2.045 * (8.4 / 30)
= 3.1363
The 95% confidence interval estimate of the sample mean is,
- E < < + E
84.25- 3.1363< <84.25 + 3.1363
81.1137< < 87.3863
( 81.1137 , 87.3863)
The 95% confidence interval estimate of the sample mean is,fall between the interval 81.1137 to 87.3863