When it comes to repeat the measure design, we have to assess the outcomes result of the test with two or more treatment conditions (Gravetter & Lockhead, 1973), in my perspective I would recommend Mary to do two conditions by using the same sample in each one to see the same outcome. The two of these conditions are high background or low background noise. In the con, having the noise will affect learning. In my view, both lessons cannot offer in the same condition because some will get advantage of learning same materials over and over will get higher scores. Some time it will be difficult if it happened at the same time to know whether student will learn due to noise background or other factor may affect the learning environment due to unknown object. Sometime different factor may contribute. For example some lesson will be harder than other if they give same score. For example, if the test offer with different version such as A and B, if B will have some difficult question than version A. in pro, it can happened that, some student may have better skills than other with same design test. In my test design, I would choose to do two different tests to see the result, one with higher background noise and other with low background noise to see the effect after students take the test from each environment.

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