Feeling thermometers measure how warmly people feel towards

Feeling thermometers measure how warmly people feel towards a person, group, or issue. They are usually measured on a scale of 0 to 100, with 100 being the warmest. Assume that voters in the United States, if asked, would give Barack Obama a mean thermometer score of 53, with a standard deviation of 19. What is the probability that a random sample of 400 voters would give him a score of 55 or above?

Solution

mu = 53, sigma =19

n =400

X>=55 is equivalent to z>= 55-53/19/rt 400 = 40/19 = 2.1053

P(Z>=2.1053) = 0.5-0.4826

= 0.0174