Question

Provide the goal of the study, clearly stating the research hypothesis. Describe the study design.

Describe the results noting the direction (e.g., higher or lower; increase or decrease; etc.) and difference between sample mean (M = ?; 95% CI = ?) and the population mean (µ = ?).

Report the inferential statistic used to compute the p-value (Z [ n = ?] = observed value, p < or > .05) and state if the results are significant or not.

Report and interpret the 95% CI around the difference between the two means (e.g., does the CI contain 0 or not—how do you interpret the Ho if it does or does not include 0?). Also, be sure to report and interpret the effect size (d = ?).

1. A research team happens to know that male rats administered a placebo drug will spend μ = 5 minutes per hour grooming (σ = 6). They believe that male rats administered a low dose of the street drug ecstasy will spend less than 5 minutes per hour grooming. They chose 100 male rats, administered a low dose of ecstasy to each, then measured the number of minutes per hour each rat spent grooming. The mean of this sample was M = 4. The research question the researcher want to answer is: does administering a low dose of ecstasy affect the time spent grooming?

Answer 1

1) H₀:

    H₁:

The test statistic z = ()/()

                             = (4 - 5)/(6/)

                             = -1.67

P-value = P(Z < -1.67)

             = 0.0475

Since the P-value is less than the significance level(0.0475 < 0.05), so we should reject the null hypothesis.At 0.05 significance level, there is sufficient evidence to conclude that a low does of ecstasy affect the time spent grooming.

At 95% confidence level, the critical value is z_0.025 = 1.96

The 95% confidence interval is

+/- z_0.025 *

= 4 +/- 1.96 * 6/

= 4 +/- 1.176

= 2.824, 5.176

Since the interval does not contain 0, so we should reject the null hypothesis.

Cohen's d =

                 = (4 - 5)/6

                 = -0.16