Question

Suppose that 40% of U.S. voters are Democrats. What is the probability that in a sample of 200 voters that at least 90 people will be a Democrat?

Answer 1

Solution :

Given that probability p =0.40

Total sample size n = 200

q = 1-0.40 = 0.60

mean = n*p = 200*0.4 = 80

Standard deviation =

The probability that at least 90 people from a sample of 200 voters will be a Democrat is

So from standard normal distribution table,

The probability that at least 90 people from a sample of 200 voters will be a Democrat is 0.9345.

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