The answer from the text shows it should be roughly 80, for some reason I keep g

Question

The answer from the text shows it should be roughly 80, for some reason I keep getting roughly 40. I previously asked this question and they got 40 as well so I was wondering if you could figure out why we are getting 40 and see if you can understand how to get the right answer.'

Thanks

7. An educational researcher wishes to estimate the difference in average scores of elementary school children on two versions of a 100-point standardized test, at 99% confidence and to within two points. Estimate the minimum equal sample sizes necessary if it is known that the standard deviation of scores on different versions of such tests is 4.9

Explanation / Answer

Here E=2, z value is 2.58 and sd=4.9

E=z*sd/sqrt(n)

So n=(z*sd/E)^2=40

As it is asked for two versions of a 100-point standardized test answer would be n+n=80

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