# A group of 50,000 tax forms has an average gross income of \$37,000,

A group of 50,000 tax forms has an average gross income of \$37,000, with an SD of \$20,000. Furthermore, 20% of the forms have a gross income over \$50,000. A group of 900 forms is chosen at random for audit.
To estimate the chance that between 19% and 21% of the forms chosen for audit have gross incomes over \$50,000, a box model is needed.

a) Should the number of tickets in the box be 900 or 50,000?
b) each ticket in the box shows a zero or a onea gross income a zero or a onea gross income
c) True or false: the SD of the box is \$20,000.
d) True or false: the number of draws is 900.
e) Find the chance (approximately) that between 19% and 21% of the forms chosen for audit have gross incomes over \$50,000. f) With the information given, can you find the chance (approximately) that between 9% and 11% of the forms chosen for audit have gross incomes over \$75,000? Either fond the chance, or explain why you need more information.