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K.Binks
 one year ago
How do I do problems like this? " The time required to finish a test is normally distributed with a mean of 60 minutes and a standard deviation of 10 minutes. What is the probability a student will finish the test between 50 and 60 minutes?"
K.Binks
 one year ago
How do I do problems like this? " The time required to finish a test is normally distributed with a mean of 60 minutes and a standard deviation of 10 minutes. What is the probability a student will finish the test between 50 and 60 minutes?"

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anonymous
 one year ago
Best ResponseYou've already chosen the best response.0You can use the standard normal distribution curve. let me see if I can find one

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0from http://www.oswego.edu/~srp/stats/6895997.htm dw:1439294802648:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Your mean is 60 and standard deviation is 10. So 60 goes in the middle and add 10 to the right, subtract 10 to the left. 34% lies between 50 and 60 dw:1439294942539:dw

K.Binks
 one year ago
Best ResponseYou've already chosen the best response.0What about the next one, where the times are 40 and 70?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0between 40 and 70, add up the percentages between those numbers

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0You can do it the way @shabbaranks is as well and use zscores. That method works for all possible values. Using the curve only works when the numbers are multiples of the standard deviation

K.Binks
 one year ago
Best ResponseYou've already chosen the best response.0Ok, just add them up, as in 34+34+13.5? I think I understand what you're saying, for both methods. I didn't know what a zscore was, but I think I get it now.

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yes that's what I meant. That's right

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I don't think they make them memorize the chart (hopefully lol) Here's one btw: http://www.regentsprep.org/regents/math/algtrig/ats7/zchart.htm

K.Binks
 one year ago
Best ResponseYou've already chosen the best response.0Ok, I think I got it now. Thank ya'll!

mathmate
 one year ago
Best ResponseYou've already chosen the best response.0@k.binks @peachpi 's method explains visually how the Zscore works, while @shabbaranks 's method gives the procedure to calculate practical problems. You're lucky to have both!
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