Probability- norm. distributed-mean 138, standard dev. 9.7  TOPIC_SOLVED

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Probability- norm. distributed-mean 138, standard dev. 9.7

Postby ShortStuff on Wed May 27, 2009 4:10 pm

The mean systolic blood pressure of adult males is normally distributed with a mean of 138 (millimeters of mercury) and a standard deviation of 9.7. What percent of adult males have blood pressure between 161.28 and 164.9?

Math is absolutely my weakest subject, and I am very lost... there is a chart for one example in our text..but I am not sure if I should use the chart to get the percentages or if there is some way to figure them that I am missing. This is what I have so far...

161.28 - 138/9.7=23.28/9.7= 2.4

164.9-138/9.7=26.9/9.7=2.77
--- I know that these are the z-scores, so how do I get the percentages from this? I know that I will have to subtract the percentages to get the answer...but I am lost on how to find the percentages...Can anyone please help!!??
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Postby stapel_eliz on Wed May 27, 2009 7:07 pm

ShortStuff wrote:161.28 - 138/9.7=23.28/9.7= 2.4

164.9-138/9.7=26.9/9.7=2.77
--- I know that these are the z-scores, so how do I get the percentages from this?

Didn't they give you a table of z-scores?

You'd probably read down the left-hand side to find "2.4" and then across in that row to find "0.00", and then take that value as the (decimal-form) percentage for the z-score of 2.40, which should be something like 0.9918. Then you'd find the row starting with "2.7" and find the entry under "0.07", which should be something like 0.9972.

Then the probability of being between the two values that generated your z-scores would be the difference of the two probabilities....

:wink:
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