Answer:
Step-by-step explanation:
Given
Solving (a): Point estimate of difference of mean
This is calculated as:
Solving (b): 90% confidence interval
We have:
Confidence level is:
Calculate
The z score is:
The endpoints of the confidence level is:
Split
Hence, the 90% confidence interval is:
Solving (c): 95% confidence interval
We have:
Confidence level is:
Calculate
The z score is:
The endpoints of the confidence level is:
Split
Hence, the 95% confidence interval is: