Question

1. an american society of investors survey found 30 percent of individual investors have used a discount broker. in a random sample of nine individuals, what is the probability: (a) exactly two of the sampled individuals have used a discount broker? (b) none of them have used a discount broker? (c) find the mean (expected value) number of individuals that use a discount broker? (d) compute the variance and standard deviation of the number of individuals that use a discount broker (use the short-cut formul

Answer 1

According to a survey by the American Society of Investors, 30% of individual investors have used a discount broker. The probability in a sample of nine people chosen at random is shown below using binomial theorem.

Used a discount broker: p(used a binomial distribution) = 0.3 Binomial Theorem:

P(x) = ncx.p^x.q^n-x

The binomial formula yields n = 9.

(a) Binompdf(9,.3, 2) =.2668 for P(x = 2).

(b) Binomcdf(9,.3, 3) =.7297 for P(x 3)

(c) Binomcdf(9,.3, 2) = 1-.4628 =.5372 where P(x 3)= 1 - P(x 2) = 1 - P(x 2).

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