Scores on a certain test are normally distributed with a variance of 14. A researcher wishes to estimate the mean score achieved by all adults on the test. Find the sample size needed to assure with 98% confidence that the sample mean will not differ from the population mean by more than 2 units.

The sample size must be 20 so that  sample mean will not differ from the population mean by more than 2 units.  

Step-by-step explanation:

We are given the following in the question:

Variance = 14

We need to form a 9% confidence interval such that sample mean will not differ from the population mean by more than 2 units.

Thus, margin of error for the confidence interval is 2.

Formula for margin of error:

Putting the values, we get,

Thus, the sample size must be 20 so that  sample mean will not differ from the population mean by more than 2 units.

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according to the triangle sum theorem, all the angles in a triangle must add up to 180 degrees. if we know one angle is already 90, we do 180-90=90. the other 2 angles must add up to 90, exactly.

step-by-step explanation: