A survey of 144 retail stores revealed that the average price of a microwave was $375 with a standard error of $20. What is the 80% confidence interval of the true average price of the microwave?
1 Answer
Nov 23, 2015
The sample size is large, so use a Standard Normal distribution ...
Explanation:
The z-values for an 80% confidence interval is
[Note: the above solution assumes that 20 is truly the standard error and not the sample standard deviation . Otherwise, divide 20 by
Hope that helped