Question

The following table shows the record of the weight of all boxes in an EMS delivery truck.

Weight of box (lb)	No. of boxes
1-10	8
11-20	7
21-40	5

a) If you randomly select 8 boxes from this truck without replacing the box after each pick, what is the probability that at least 6 of them are 10 pounds or lighter?

b) If you randomly select 8 boxes from this truck with replacing the box after each pick, what is the probability that at least 6 of them are 10 pounds or lighter?

Answer 1

a) If we randomly select 8 boxes from this truck without replacing the box after each pick, the probability that at least 6 of them are 10 pounds or lighter = + + = 0.1212 + 0.0303 + 0.0043 = 0.1558

b) If we randomly select 8 boxes from this truck with replacing the box after each pick, the probability that at least 6 of them are 10 pounds or lighter = + + = 0.0348 + 0.0199 + 0.0114 = 0.0661