Nt1310 Unit 1 Case Study

Homework 4.3 #21
43% of adults in the US receive fewer than 5 phone calls a day. In a random sample of 7 adults, what is the probability that the number receiving fewer than five calls a day is (a) exactly 3 (b) at least 3 (c) more than 3?

n p 7 0.43 x P(Exactly x) P(At most x) P(At least x)
0 0.0195 0.0195 1.0000
1 0.1032 0.1228 0.9805
2 0.2336 0.3564 0.8772
3 0.2937 0.6502 0.6436
4 0.2216 0.8718 0.3498
5 0.1003 0.9721 0.1282
6 0.0252 0.9973 0.0279
7 0.0027 1.0000 0.0027

I plugged in the given percentage of adults (43%) into the “p” section of the table and the random sample size into the “n” section of the table and hit enter to have excel do the calculations.
In a random sample of 7 adults, the probability of the number of adults receiving fewer than five calls a day being exactly 3 is 29.37%.
In a random sample of 7 adults, the probability of the number of adults receiving fewer than five calls a day being more than 3 is