It is fairly common for people to put on weight when they quit smoking. While a small weight gain is normal, excessive weight gain can create new health concerns that erode the benefits of not smoking. The accompanying table shows a portion of the weight data for 50 women before quitting and six months after quitting; the complete data set, labeled Smoking_Weight, are available on the text website.

Weight after Quitting Weight before Quitting

155..............140

142..............144

: .............. :

147..............135

a. Construct and interpret a 95% confidence interval for the mean gain in weight.

b. Use the above confidence interval to determine whether or not the mean gain in weight is 5 pounds.