SOLUTION: A Social Media Online Platform claims that 65% of the companies who advertise using their online platform have growth in sales revenue within 1 week of the first appearance of the

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Question 1150681: A Social Media Online Platform claims that 65% of the companies who advertise using their online platform have growth in sales revenue within 1 week of the first appearance of the advertisement. What is the probability that among 80 randomly selected companies who advertise on “Facebooked”, at most 47 of them have growth in sales revenue within 1 week of the first appearance of the advertisement?
Answer by VFBundy(438) About Me  (Show Source):
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n = 80
p = 0.65
q = 0.35

M = np = 80(0.65) = 52

SD = sqrt%28n%2Ap%2Aq%29 = sqrt%2880%2A%280.65%29%2A%280.35%29%29 = sqrt%2818.2%29 = 4.266

"At most 47" means 47 or fewer.

P(x <= 47) ---> P(x < 47.5)

z = %2847.5+-+M%29%2F%28SD%29 = %2847.5+-+52%29%2F%284.266%29 = %28-4.5%29%2F%284.266%29 = -1.05

Look up -1.05 on a z-table. The result is 0.1469. So, there is a 0.1469 chance that at most 47 companies have growth in sales revenue within one week of the first appearance of the advertisement.