Posted by **Heidi** on Wednesday, July 9, 2014 at 4:32pm.

The probability the New Year's day is on Saturday is a randomly chosen year is 1/7.

15 years was chosen randomly. Find the probability that,

(1) Exactly four of these years have a New Year's day on a Saturday.

(2) At least two of these years have New Year's day on a Saturday.

- Statistics/Probability -
**Reiny**, Wednesday, July 9, 2014 at 5:19pm
prob(Saturday) = 1/7

prob(not Saturday) = 6/7

prob(exactly 4 of 15 years is a Saturday)

= C(15,4) (1/7)^4 (6/7)^11

= appr .1043

at least 2 Saturdays ----> 1 - (case of 0 Saturday + case of 1 Saturday)

= 1 - (6/7)^15 - C(15,1)(1/7)(6/7)^14

= .6534

check my arithmetic

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