The Professor's Response

Hiii Professor

I was wondering if you could tell me why in question #32 in chapter 9 are the signs not equal? I don't know if I'm reading it wrong, or maybe I'm not understanding

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Professor McGukian

Hi Sandra,

Here is the key sentence to determine the claim, "Use the results below and a 2% significance level to test the claim that the program produces some change in the student’s ability to spot errors in written work."

If the program did not produce a change in the student's ability, you would say the before and after means are equal wouldn't you? You would have to because no change would mean the before and after are the same. This claim doesn't say there will be no change, it says there will be a change. Thus, the the mean before is not the same as the mean after (i.e., µbefore ≠ µafter). "Some change," does not imply an improvement necessarily, so don't make the mistake of assuming the change has to be for the better.

Hope that helps,

Professor McGuckian

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