Steve believes that his wife’s cell phone battery does not last
as long as his cell phone battery. On ten different occasions, he
measured the length of time his cell phone battery lasted and
calculated that the mean was 17.7 hours with a standard deviation
of 3.2 hours. He measured the length of time his wife’s cell phone
battery lasted on six different occasions and calculated a mean of
18.8 hours with a standard deviation of 7.5 hours. Assume that the
population variances are the same. Let Population 1 be the battery
life of Steve’s cell phone and Population 2 be the battery life of
his wife’s cell phone. Step 1 of 2 : Construct a 95% confidence
interval for the true difference in mean battery life between
Steve’s cell phone and his wife’s. Round the endpoints of the
interval to one decimal place, if necessary.