## Question 868:

Asked on October 14, 2010

Tags:
Confidence Intervals ,
Margin of Error

1

## Answer:

No answer provided yet.Because most confidence intervals are symmetric we can work backwards and find the mean. Typically a confidence interval is constructed by adding and subtracting the margin of error. We don't know the margin of error but we do know the width of the confidence interval. It is 30 points wide (150-120). So we know then that the margin of error is half that amount or 15. The sample mean is therefore 150-15 = 135.