I know this is probably a really simple question, but no matter what I do I get the wrong answer! =[
So if anybody can help, that'd be great.
A laboratory measurement system used to measure blood potassium levels has a standard deviation of *sigma* = 0.2 mEq/dl in repeated testing. Repeated readings are normally distributed with mean equal to the true potassium level in the blood sample. How many times should the blood samples be tested for one person to get a margin of error no larger than *plus/minus* 0.15 mEq/dl with 95% confidence?
So if anybody can help, that'd be great.
A laboratory measurement system used to measure blood potassium levels has a standard deviation of *sigma* = 0.2 mEq/dl in repeated testing. Repeated readings are normally distributed with mean equal to the true potassium level in the blood sample. How many times should the blood samples be tested for one person to get a margin of error no larger than *plus/minus* 0.15 mEq/dl with 95% confidence?