Question 1202944: The mean amount of time it takes a kidney stone to pass is 12 days and the standard deviation is 4 days. Suppose that one individual is randomly chosen. Let X = time to pass the kidney stone. Round all answers to 4 decimal places where possible.
What is the minimum number of days for the upper quarter of the time to pass a kidney stone ?
Answer by ikleyn(52777)   (Show Source):
You can put this solution on YOUR website! .
The mean amount of time it takes a kidney stone to pass is 12 days
and the standard deviation is 4 days. Suppose that one individual is randomly chosen.
Let X = time to pass the kidney stone. Round all answers to 4 decimal places where possible.
What is the minimum number of days for the upper quarter of the time to pass a kidney stone ?
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A normal curve is a bell-shaped.
In this problem, they want you determine a raw mark x on the time axis
such that the area under the given normal curve on the right of this mark is 1/4.
It is the same as to find a raw mark x on the time axis
such that the area under the given normal curve on the left of this mark is 3/4, or 0.75.
For this purpose, you may use the standard function invNorm in your regular calculator
TI-83 or TI-84
area mean SD <<<---=== formatting pattern.
P = invNorm(0.75, 12, 4).
It gives the ANSWER P = 14.698
In my opinion, the request (the instruction in the post) to provide an answer with
4 decimal places is non-sensical and shows absence of common sense.
In such problems, one decimal place is enough.
Solved.
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Alternatively, you may use an online free of charge calculator
https://onlinestatbook.com/2/calculators/inverse_normal_dist.html
If you are a beginner student, I insistently recommend you to play with this online calculator.
It has convenient, intuitively clear interface and shows the area of interest,
so you quickly will learn the subject, the meaning and the technique of these calculations and will be happy.
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