Posted by **anna** on Friday, November 23, 2012 at 11:05am.

3. A researcher is interested in whether listening to music helps or hinders test-performance. To control for differences in cognitive level, this researcher decides to use a within-participants design. He selects a random sample of participants and has them study different material of equal difficulty in both the music and no music conditions. Participants take a 20-item quiz on the material. The table below shows the scores on the quiz. The study is completely counterbalanced to control for order effects. The scores obtained are measured on an interval-ratio scale and are normally distributed.

Music No Music

17 17

16 18

15 17

16 17

18 19

18 18

a. What statistical test should be used to analyze the data?

b. Is this a one- or two tailed test?

c. Identify H0 and Ha for this study.

d. Conduct the appropriate analysis. Should H0 be rejected? What should the researcher conclude?

e. Calculate the 95 confidence interval.

- stat and research -
**tristian**, Friday, November 23, 2012 at 11:16am
C. Identify H0 and Ha for this study.

- stat and research -
**PsyDAG**, Friday, November 23, 2012 at 12:13pm
It would help to use the same name.

"whether listening to music *helps or hinders* test-performance"

Ho: mean music = mean no music

Ha: mean music ≠ mean no music

How many tails would that have?

Find the mean first = sum of scores/number of scores

Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.

Standard deviation = square root of variance

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n

If only one SD is provided, you can use just that to determine SEdiff.

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to your Z score.

I'll let you do the calculations.

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