leakage from underground gasoline tanks at service stations

leakage from underground gasoline tanks at service stations can damage the environment. It is estimated that 25% of these tanks leak. You examine 15 tanks chosen at random, independently of each other.

A) what is the mean number of leaking tanks in such samples of 15%?

B) What is the probability that 10 or more of the 15 tanks leak?

C) Now you do a larger study, examining a random sample 1000 tanks nationally. What is the probability that at least 275 of these tanks are leaking?

Solution

B) Go to TI83>2ND (DISTR)>binomcdf( and enter 15, 0.67,10 and the result is 0.585.

C) Go to TI83>2ND (DISTR)>binompdf( and enter 1000,0.275,275 and the result is 0.282.