Question

if a toaster ovens hav an average life expectancy of 9.5 years with a standard deviation of 4.75 years. what is the probability that a toaster oven will last twenty years or will fail in one year or less?

Answer 1

Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability for each Z score.