Finding Percentage with 68-95-99.7 rule

unreal030

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Aug 31, 2007
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I cannot figure out how to do this problem. (C) and (D). I know how to find lowest percentage out of a total and between two z-score points and the like. However I do not know how to use the 68-95-99.7 rule to find a "less percentage" below a specific observation point such as 99.7 furthermore, I am confused by how I find the actual percentage vs. this other percentage (which apparently isn't the actual...)

4. Winter Olympics 2002 downhill. Fifty-three men qualified for the men's alpine
downhill race in Salt Lake City. The gold medal winner finished in 1 minute 39.13
seconds. All competitors' times (in seconds) are found in a JMP data le called
downhill.JMP.

(c) If the Normal distribution is appropriate to describe the downhill race times,
what percentage of times will be less than 99.7 seconds? Use the 68-95-99.7
rule to answer this question.
(d) What is the actual percentage of times less than 99.7 seconds?

 Note, this 99.7 corresponds to an actual race time of interest and should not be
confused with the 99.7 from the 68-95-99.7 rule.
 
Unfortunately, we do not have access to the chart downhill.jmp

From this I assume we can find the mean and standard deviation.
 
I have attached a the downhill jmp here. I am still not able to figure out how to do this problem so further help would greatly be appreciated.
 

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