One of your employees has suggested that your company develop a new product. A survey is designed to study whether or not there is interest in the new product. The response is on a 1 to 5 scale with 1 indicating definitely would not purchase, · · ·, and 5 indicating definitely would purchase. For an initial analysis, you will record the responses 1, 2, and 3 as No, and 4 and 5 as Yes. a. 5 people are surveyed. What is the probability that at least 3 of them answered Yes b. 100 people are surveyed. What is the approximate probability that between 45% to 52% of people answered Yes? For part a) There are 5 choices that people can respond by 1, 2 ,3 ,4 and 5. Since 1, 2 and 3 are considered "No", the probability of someone answering "No" is 3/5. For choices 4 and 4, the probability of someone

Aryanna Blake

Aryanna Blake

Answered question

2022-10-29

One of your employees has suggested that your company develop a new product. A survey is designed to study whether or not there is interest in the new product. The response is on a 1 to 5 scale with 1 indicating definitely would not purchase, · · ·, and 5 indicating definitely would purchase. For an initial analysis, you will record the responses 1, 2, and 3 as No, and 4 and 5 as Yes.
a. 5 people are surveyed. What is the probability that at least 3 of them answered Yes?
b. 100 people are surveyed. What is the approximate probability that between 45% to 52% of people answered Yes?
For part a) There are 5 choices that people can respond by 1, 2 ,3 ,4 and 5. Since 1, 2 and 3 are considered "No", the probability of someone answering "No" is 3/5. For choices 4 and 4, the probability of someone responding with that is 2/5.
This looks like it fallows a binomial distribution so I calculated the probability of P(3) + P(4) + P(5).
However for part b), I'm confused. I can calculate the probability of someone saying yes but I don't know how to calculate the probability that a percentage of people saying yes. Does anyone know how to approach this question? I though about using the Z table, but that already calculates area.

Answer & Explanation

Alannah Yang

Alannah Yang

Beginner2022-10-30Added 22 answers

Let X denote the number of people answering yes. Then X is a bionomial random variable.
Let n denote the number of trials (i.e. people surveyed). Let p denote the probability of a yes-response on a given trial, and let q denote the probability of a no-response. Then, as you've argued, we have
p = 2 / 5 , q = 3 / 5.
Then in part (a), the probability of at least three people answering yes is
P ( x = 3 ) + P ( x = 4 ) + P ( x = 5 ) = .
So far so good!
Now for part (b):
You see, 45 of 1000 is 450, and 52 of 1000 is 520. So I reckon the probability you want is
P ( X = 450 ) + P ( X = 451 ) + + P ( X = 520 ) = r = 450 520 P ( X = r ) = r = 450 520 ( 1000 r ) ( 2 5 ) r ( 3 5 ) 1000 r =

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