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ajricherson09 ajricherson09
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Posts: 7
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8 years ago
A popular retail store knows that the purchase amounts by its customers is a random variable that follows a normal distribution with a mean of $30 and a standard deviation of $9.

What is the probability that a randomly selected customer will spend $30 or more at this store? Place your answer, rounded to 4 decimal places, in the blank. For example, 0.3456 would be a legitimate entry

The percent defective for parts produced by a manufacturing process is targeted at 4%. The process is monitored daily by taking samples of sizes n = 160 units. Suppose that today’s sample contains 14 defectives.

Determine a 95% confidence interval for the proportion defective for the process today.

Place your LOWER limit, rounded to 3 decimal places, in the first blank. For example, 0.123 would be a legitimate answer. 

Place your UPPER limit, rounded to 3 decimal places, in the second blank. For example, 0.345 would be a legitimate entry. 

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wrote...
Educator
8 years ago
A popular retail store knows that the purchase amounts by its customers is a ran
ajricherson09 Author
wrote...
8 years ago
Thank you, I ended up entering .50 since my mean was $30 and the chance that someone would spend $30 or more could be 50%
wrote...
8 years ago Edited: 8 years ago, metal_zelda
Thank you, I ended up entering .50 since my mean was $30 and the chance that someone would spend $30 or more could be 50%
The modifier is "or more," which makes this answer highly unlikely. The procedure detailed in bio_man's post is one of many ways of dealing with the probability density of normal distributions.

Edit: Oops, misread the question in the linked post. You aren't given an interval, so you'd probably need to do tail probability.
Post Merge: 8 years ago

.
Post Merge: 8 years ago

Actually, I changed my mind on this one-- 50% seems reasonable
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