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Samples and Probability

I have a population of 100, mean of 500 and standard deviation of 100. I am asked what range of values should contain the sample mean 90% of the time.

I have calculated the standard error =10.

I don't know what figure to use in the z scores tables, column d. 1/2 of 90% is 45% or .4500. My choices in column D are .4495 or .4505. Which is correct? How do I know which one to use?

Solution Preview

45% is equal to 0.45. Since the normal table is given for probability which lies between 0 to 1, you need to look for 0.45 in ...

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