A study estimates the mean annual family income for families living in public housing in Chicago. For a random sample of 30 families, the annual incomes (in hundreds of dollars) are 83 90 77 100 83 64 78 92 73 122 96 60 85 86 108 70 139 56 94 84 111 93 120 70 92 100 124 59 112 79.

(a) Construct a stem-and-leaf plot of the incomes. What do you predict about the shape of the population distribution?

(b) Find and interpret point estimates of and or, the population mean and standard deviation.

(c) Construct and interpret a 95% confidence interval for