3.) Bob works as a telemarketer. Based on his previous call records, he stands a

Question

3.) Bob works as a telemarketer. Based on his previous call records, he stands a 3.8% chance of making a sale in a week. If Bob calls 40 people, what is the probability that at least one sale will result from the calls?

a. 0.66
b. 0.21
c. 0.34
d. 0.45
e. 0.55

4.) Samantha takes an aptitude test and manages to answer 15 questions of a True-False quiz by picking an arbitrary choice. She will be able to clear the test only if she gets ten or more correct answers. What is the probability that Samantha will clear the test?
a. 0.94
b. 0.06
c. 0.09
d. 0.85
e. 0.15

Explanation / Answer

3 ANS) Let X be the number of sales

This is a binomial random variable with n = 40 and p = 3.8% =0.038 ATLEAST [ = 1- 0.038= 0.962]

. Thus

P[ X 1 ] = 1 - P[ X = 0 ] = 1- [ 1-0.962] ^40

= 1- 0.787 = 0.123

SO OPTION IS B

4 ANS )

Chance of getting 10 right: 0.5^15 * C(15,10) = 0.09

Chance of getting 11 right: 0.5^15 * C(15,11) = 0.04

Chance of getting 12 right: 0.5^15 * C(15,12) = 0.013

Chance of getting 13 right: 0.5^15 * C(15,13) = 0.003

Chance of getting 14 right: 0.5^15 * C(15,14) = 0.0004

Chance of getting 15 right: 0.5^15 * C(15,15) = 0.00003
Chance of any of the above happening:
0.09 + 0.04 +0.013 + 0.003 + 0.0004+ 0.00003= 0.150

ANSWER IS OPTION E

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