Posted by **Anonymous** on Thursday, September 23, 2010 at 8:32pm.

Twenty students randomly assigned to an experimental group receive an instructional program; 30 in a control group do not. After 6 months, both groups are tested on their knowledge. The experimental group has a mean of 38 on the test (with an estimated population standard deviation of 3); the control group has a mean of 35 (with an estimated population standard deviation of 5). Using the .05 level, what should the experimenter conclude?

- Psychology -
**PsyDAG**, Friday, September 24, 2010 at 2:40am
Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√(n-1)

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.

- Psychology -
**Mrs. Nation**, Friday, November 30, 2012 at 7:25pm
(a) and (c)

Ho: u(ex) - u(ct) = 0

Ha:u(ex) – u(ct) is not equal to 0

Test stat: t = (38-35) / sqrt[9/20 + 25/30] = 2.6482

p-value = 2*P(t > 2.6482 with df = 48) = 0.0109

Conclusion:

At the 5% significance level, reject Ho because the p-value is less than 5%

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