Statistical Math?

The Board of Realtors of a small city reports that 80% of the houses that are sold have


been on the market for more than 6 months. The Board takes a random sample of 15


homes that have recently been sold and counts the number that were on the market for


more than 6 months. What is the Probability that of 15 homes in the sample:





a. less than 12 have been on the market for more than 6 months?


b. between 8 and 13 have been on the market for more than 6 months?


c. at least 10 homes have been on the market for more than 6 months?


d. at most 4 have been on the market for more than 6 months?

Statistical Math?
note:


binomial distribution: P(x=k) = 15Ck (0.8)^k (0.2)^(15-k)


this is the probability that k of the houses have been on the market for more than 6 months.





a. 1 - P(x=12) - P(x=13) - P(x=14) - P(x=15)





b. P(x=8) + P(x=9) + P(x=10) + P(x=11) + P(x=12) + P(x=13)





c. P(x=10) + P(x=11) + P(x=12) + P(x=13) + P(x=14) + P(x=15)





d. P(x=0) + P(x=1) + P(x=2) + P(x=3) + P(x=4)








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