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jlh_05 · Oct 1, 2007, 08:14 AM

The Master Card center of a bank in Calgary has found that 62 percent of cardholders pay their new monhly balance in full before the payment due date. Suppose the credit center selects four cardholders at random.
Use this information to answer the following questions.

a) What is the probability that all four cardholders will pay their new monthly balance in full before the payment due date?

b) What is the probability that at least three of them will pay their new monthly balance in full before the payment due date?
:confused: :confused:

galactus · Oct 1, 2007, 02:54 PM

This is just binomial probability

#1: $C(4,4)(.62)^{4}(.38)^{0}$

#2: $\sum_{k=3}^{4}C(4,k)(.62)^{k}(.38)^{4-k}$

katringette22 · Oct 1, 2007, 03:22 PM

could you do it the lazy way : 62/100 because its 62 of 100 which therefor could equal x/4
then you multiply 62 by 4 then divid it but one hunder

then do the same for 3 by just use the number 3 insead of 4

galactus · Oct 2, 2007, 06:12 AM

No, but if you notice #1 boils down to $(0.62)^{4}$

The other one you need to add them for the 3 and 4 cases.

$C(4,3)(0.62)^{3}(0.38)+C(4,4)(0.62)^{4}$