Foundation

A bag has 3 red, 4 green and 5 blue balls (12 total). One ball is removed at random and is blue. A second ball is then removed. Find P(second ball is red given the first ball was blue).

A quality inspector samples 120 items from a batch of 15000 and finds 3 defective, but the sample was taken only from items made in the last hour of the day. Explain why her estimate might not be reliable, and give the estimate assuming the sample were representative.

Data on 200 students' exam scores is in a spreadsheet. Give one advantage of using a spreadsheet rather than calculating the mean and range by hand.

A youth club has 45 members under 13 and 75 members aged 13 to 17 (120 total). A stratified sample of 40 members is needed. How many aged 13 to 17 should be sampled?

A company pilots its customer feedback survey on 20 customers before sending it to all 5000 customers. Explain why using only 20 people is still useful.