In: Statistics and Probability
In engineering and product design, it is important to consider the weights of people so that airplanes or elevators aren't overloaded. Based on data from the National Health Survey, we can assume the weight of adult males in the US has a mean weight of 197 pounds and standard deviation of 32 pounds. We randomly select 64 adult males. What is the probability that the average weight of these 64 adult males is over 192 pounds? Give your answer to 4 decimal places. For help on how to input a numeric answer, please see "Instructions for inputting a numeric response."
My answer was 0.1056 but it marked it incorrect? Please tell me why and show the work. thanks
Solution :
mean = = 197
standard deviation = = 32
n = 64
= = 197
= / n = 32 / 64 = 4
P( > 192) = 1 - P( < 192)
= 1 - P[( - ) / < (192 - 197) / 4]
= 1 - P(z < -1.25)
Using z table,
= 1 - 0.1056
= 0.8944