Question
a study shown that 20% of all college textbooks cost at least $70.it is known that the standard deviation of the prices of all college textbook is $9.50.assuming that prices of all college textbooks follow a normal distribution, find the mean price of all college textbooks.
Answers
bobpursley
http://www.jiskha.com/display.cgi?id=1369182329
Put in this applet the standard deviation, then the mean as zero.
Then start at -6, check the area. EVentually, you will get an area of .20
Then, say -6.5 is the point, you know that is really 70, so add 70 +6.5, and you have the mean.
Put in this applet the standard deviation, then the mean as zero.
Then start at -6, check the area. EVentually, you will get an area of .20
Then, say -6.5 is the point, you know that is really 70, so add 70 +6.5, and you have the mean.
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