Suppose you are told that a 95 confidence interval for the a

Suppose you are told that a 95% confidence interval for the average price of a gallon of regular gasoline in your state is from $3.20 to $4.20. Use the fact that the confidence interval for the mean is in the form x E to x + E to compute the sample mean and the maximal margin of error E. (Round your answers to two decimal places.)

Solution

L = lower bound of confidence interval= 3.20
U = upper bound of confidence interval =4.20

So,

x-E= 3.20

x+E=4.20

Add these equation

2x=7.40

x=3.70

So, the sample mean is $3.70

x-E=3.20

3.70-E=3.20

E=0.50

THe margin of error is $0.50