Statistics Standard Deviation Help
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Statistics Standard Deviation Help

[From: ] [author: ] [Date: 11-10-20] [Hit: ]
04*0.8416 = 19.......
"According to a survey, only 20% of customers who visited the web site of a major retail store made a purchase. Random samples of size 100 are selected.

a. What is the standard deviation of all the sample proportions of customers who will make a purchase after visiting the web site?

b. 80% of the samples will have more than what percentage of customers who will make a purchase after visiting the web site?"

For part a I did the following
sqrt((.20)*(1-.20)/100) = .04 (I don't know if this is right)

For part b I am lost for how to approach the problem.

Any help is greatly appreciated, I changed the numbers from the ones on my work so I am looking more for how to solve these than the answers themselves, thanks!

-
a. ok !

b. z-score for top 80% = - 0.8416, % of customers = 20 - 0.04*0.8416 = 19.966%
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