Answer:
Step-by-step explanation:
Given : Sample size : n= 9
Degree of freedom = df =n-1 =8
Sample mean :
sample standard deviation :
Significance level ;
Since population standard deviation is not given , so we use t- test.
Using t-distribution table , we have
Critical value =
Confidence interval for the population mean :
90% confidence interval for the mean value will be :
Hence, the 90% confidence interval for the mean value=