A Researcher Conducts an Independent-Measures Study Examining How the Brain

A researcher conducts an independent-measures study examining how the brain chemical serotonin is related to aggression.One sample of rats serves as a control group and receives a placebo that does not affect normal levels of serotonin.A second sample of rats receives a drug that lowers brain levels of serotonin.Then the researcher tests the animals by recording the number of aggressive responses each of the rats display.The data are as follows. $\begin{array}{ll}\text { Control } & \text { Low Seroto } \\\mathrm{n}=10 & \mathrm{n}=15 \\\mathrm{M}=14 & \mathrm{M}=19 \\\mathrm{SS}=180.5 & \mathrm{SS}=130.0\end{array}$
a. Does the drug have a significant effect on aggression? Use an alpha level of .05, two tails.
b. Compute Cohen's d to measure the size of the treatment effect.

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a.H0: µ1 µ2 = 0 (no effect).With df = 23...

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