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.

b

step-by-step explanation:

a difference is the result of subtraction. while each of these expressions has subtraction in it, a difference will be the result when subtraction is the last operation applied in the order of operations for the expression. this means subtraction must be outside of the parenthesis. only b has this.

hi! i think the answer is 1/2 : )