Question 1177779: A brokerage survey reports that 30 per cent of individual investors have used a discount broker, that is, one which does
not charge the full commission. In a random sample of 9 individuals, what is the probability that
a. Exactly two of the sampled individuals have used a discount broker,
b. Not more than three have used a discount broker,
c. At least three of them have used a discount broker.
Answer by ewatrrr(24785)   (Show Source):
You can put this solution on YOUR website!
Hi
Binomial Distribution: p(used a discount broker) = .3
Binomial Theorem: 
Using TI or similarly an inexpensive calculator like a Casio fx-115 ES plus
n = 9
(a) P(x = 2) = binompdf(9, .3, 2) = .2668
(b) P(x ≤ 3) = binomcdf(9, .3, 3) = .7297
(c) P(x ≥ 3)= 1 - P(x ≤ 2) = 1 - binomcdf(9, .3, 2) = 1-.4628 = .5372
Important You are comfortable using Your Calculator.
by hand:  = .2668
in b for ex: P(x=0) + P(x=1) + P(x=2) + P(x=3)
The Calculator does these computations and additions for you
when using the binomcdf function. My recommendations is USE your calculator.
Wish You the Best in your Studies.
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