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aleksley [76]
3 years ago
9

Assume that 8​% of people are​ left-handed. We select 6 people at random. ​a) How many lefties do you​ expect? ​b) With what sta

ndard​ deviation? ​c) If we keep picking people until we find a​ lefty, how long do you expect it will​ take?
Mathematics
1 answer:
klemol [59]3 years ago
4 0

Answer:

a) 0.48

b) 0.6645

c) 12.5

Step-by-step explanation:

For each person, there are only two possible outcomes. Either they are left-handed, or they are not. The probabilities of each person being left-handed are independent. So we use the binomial probability distribution to solve this question.

Binomial probability distribution

Probability of exactly x sucesses on n repeated trials, with p probability.

The expected value of the binomial distribution is:

E(X) = np

The standard deviation of the binomial distribution is:

\sqrt{V(X)} = \sqrt{np(1-p)}

The number of trials expected to find r sucesses is given by

N = \frac{r}{p}

In this problem we have that:

Assume that 8​% of people are​ left-handed. We select 6 people at random. ​

This means that p = 0.08, n = 6

a) How many lefties do you​ expect?

E(X) = np = 6*0.08 = 0.48

​b) With what standard​ deviation?

\sqrt{V(X)} = \sqrt{np(1-p)} = \sqrt{6*0.08*0.92} = 0.6645

​c) If we keep picking people until we find a​ lefty, how long do you expect it will​ take?

Number of trials to find 1 success. So

N = \frac{r}{p} = \frac{1}{0.08} = 12.5

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