Statistics: Mrs B's cholesterol level is higher than only 15% of females aged >= 50

[strugglingandinneed]

Statistics: Mrs B's cholesterol level is higher than only 15% of females aged >= 50

According to her doctor, Mrs. Brown's cholesterol level is higher than only 15% of the females aged 50 and over. The cholesterol levels among females aged 50 and over are approximately normally distributed with a mean of 235 mg/dL and a standard deviation of 25 mg/DL. What is Mrs. Brown's cholesterol level? Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

 

[Deleted member 4993]

According to her doctor, Mrs. Brown's cholesterol level is higher than only 15% of the females aged 50 and over. The cholesterol levels among females aged 50 and over are approximately normally distributed with a mean of 235 mg/dL and a standard deviation of 25 mg/DL. What is Mrs. Brown's cholesterol level? Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.

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[HallsofIvy]

Do you know what a "normal distribution" is? You are told that mean is 235 with standard deviation 25 so if Mrs. Brown's cholesterol level is "x" then the corresponding "standard variable" is \(\displaystyle z= \frac{x- 235}{25}\). Now look up the z that corresponds to "15%"= 0.15 on a table of the Standard Normal Distribution. There is probably one in your textbook. Or there is one on line at http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf.

Once you have looked up that z value, solve \(\displaystyle \frac{x- 235}{25}= z\) for x.