a)For the t distribution with 15 degrees of freedom, calculate
P(T < 0.691).
b)Consider the population of electric usage per month for
houses. The standard deviation of this population is 132
kilowatt-hours. What is the smallest sample size to provide a 90%
confidence interval for the population mean with a margin of error
of 34 or less? (Enter an integer number.)
c)In order to estimate the average electric usage per month, a
sample of 47 houses were selected and the...