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Topic: Moore and McCabe Question
Replies: 1   Last Post: Oct 28, 1996 10:02 AM

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John Burnette

Posts: 161
Registered: 12/6/04
Moore and McCabe Question
Posted: Oct 28, 1996 3:06 AM
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In the probability chapter, there is a question having to do with taking a
poll about people who job. (p=.15) The poll is of 1500 people and the
question states the average percent who job of the sample should be .15
with a standard deviation of .0092 It goes on to ask something else.

Thing is, though, since I know I'm about to ask questions regarding
standard deviation of a repeated trial, I attempted to calculate the
standard deviation myself. I don't get this value.

variance of one trial = (0-.15)^2 (.85)+(1-.15)^2 (.15)=.958375
SD of one trial = .978966

sd of 1500 trials = .02528

On a related question: I was attempting to calculate the probability of not
losing money after betting craps 1000 times.

I found the odds of winning one bet was 49.292... As before I calculated the sd

mean = -.01414...

var = (-1+.01414)^2 (1-.4929292)+ (1+.014141)^2 (.49292929) = .9998

sd = .9999

sd 1000 bets = .03162

Zscore of losing money= (0 - (-.01414))/.03162 = .4472 (I can't remember
what percent this came out to but it was surprisingly low to me, I thought
it would be a much more of a sure thing.) Am I missing something?

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