Help me with Math

[Ronith]

A study published in a consumer magazine indicated that when a husband and a wife shop for a car, the husband exerts the primary influence in the descision 70% of the time. Five couples who will be purchasing a car are selected at random. Determine the probability of:

a) In exactly two of the couples, the husband will exert the primary influence on the decision.

b) In all five couples, the husband will exert the primary influence on the decision.

I got for a).132 and for b).168 ...is this correct? I dont have an answer key to check.

[Kristin]

Ronith
Ana just told me on skype to tell you that you're right. :D

[Prince]

I got something different for a?

a) 0.7 x 0.7 x 0.3 x 0.3 x 0.3 = 0.01323

b is correct, though.

b) 0.7^5 = 0.16807

[bamag]

I got something different for a?

a) 0.7 x 0.7 x 0.3 x 0.3 x 0.3 = 0.01323

b is correct, though.

b) 0.7^5 = 0.16807

Both are correct. For a), you get the answer by using binomial probability density function. (5C2) * (.7^2) * (.3^3) = .132

[Prince]

Both are correct. For a), you get the answer by using binomial probability density function. (5C2) * (.7^2) * (.3^3) = .132

Ah, of course. Because it doesn't state which two couples.