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matched-subjects design and a repeated-measures design

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1. For the following studies, indicate whether or not a repeated-measures t test is the appropriate analysis. Explain your answers.
a. A teacher is evaluating the effectiveness of a new computer training program for third-grade mathematics. One of the third-grade class gets regular instruction for 90 minutes each day. A second class gets the regular instruction 4 days each week, but on the fifth day spends 90 minutes working with the computer program. At the end of the school year, the teacher compares test scores for two classes.
b. A researcher is examining how light intensity influences color perception. A sample of 50 college students is obtained and each student is asked to judge the differences between color patches under conditions of bright light and dim light.
c. A research study compares problem-solving ability for participants with two different levels of self-esteem-high self-esteem and low self-esteem.

2. What is the primary advantage of a repeated-measures design over an independent-measures design?

3. Explain the difference between a matched-subjects design and a repeated-measures design

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T-test for two related samples; benefits of eating oatmeal; studies of visual images

1. Conduct an experiment comparing two treatment conditions which contain data with 10 scores for each treatment condition.
a) how many subjects participated in the experiment if an independent-measure design was used?
b) how many subjects participated in the experiment if a repeated-measures design was used?
c) how many subjects participated in the experiment if a matched-subjects design was used?

2. A researcher for a cereal company wanted to demonstrate the health benefits of eating oatmeal. A sample of 9 volunteers was obtained and each participant ate a fixed diet without any oatmeal for 30 days. At the end of the 30-day period, cholesterol was measured for each individual. Then the participants began a second 30-period in which they repeated exactly the same diet except that they added 2 cups of oatmeal each day. After the second 30-day period, cholesterol levels were measured again. The scores for the 9 participants are as follows: 0, -2, -11, -15, -12, +13, -9, -9, -8(negative scores indicates a decrease in cholesterol level). Are the data sufficient to demonstrate a significant change in cholesterol level after 30 days with an oatmeal diet? Use a two-tailed test with a=.05

3. Two studies on visual images were conducted. One study participants watched a screen, looking for brief presentations of a small blue arrow. The other study participants were asked to form a mental image. The results show that participants made more errors while forming images than while not forming images. Do the data indicate a significant difference between the two conditions? Use a two-tailed test with a=.05

Participants Error with Image Error without Image
A 14 4
B 9 2
C 12 10
D 7 8
E 10 6
D 8 6

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