The Edison Electric Institute has published figures on the number of kilowatt hours

used annually by various home appliances. It is claimed that a vacuum cleaner uses

an average of 46 kilowatt hours per year. If a random sample of 12 homes included

in a planned study indicates that vacuum cleaners use an average of 42 kilowatt

hours per year with a standard deviation of 11.9 kilowatt hours, does this suggest

at the 0.05 level of significance that vacuum cleaners use, on average, less than 46

kilowatt hours annually? Assume the population of kilowatt hours to be normal. how much is critical region