Question

A researcher wants to evaluate the pain relief effectiveness of a new medication for chronic pain...

A researcher wants to evaluate the pain relief effectiveness of a new medication for chronic pain sufferers. Using a pain scale from 0 to 10 (where 0 = no pain at all, and 10 = the most pain you can imagine), she compares the pain level for a sample of n1 = 4 people who received the new medication, with the pain level for a sample of n2 = 4 people who received a placebo. The data are as follows:

Medication      Placebo
7      6
4      7
6      9
4      7

(a) Identify the Independent Variable (IV):

Pain level

People taking placebo  

  People taking medication

Medication type

(b) Identify the Dependent Variable (DV):

Pain level

People taking placebo   

People taking medication

Medication type

(c) What is the null hypothesis (H0) for a two-tailed test?

μ1 - μ2 ≥ 0

μ1 - μ2 ≤ 0

   μ1 - μ2 = 0

μ1 - μ2 ≠ 0

(d) What is the alternative hypothesis (H1) for a two-tailed test?

μ1 - μ2 > 0

μ1 - μ2 < 0

   μ1 - μ2 = 0

μ1 - μ2 ≠ 0


(e) Compute df for an independent t test.

df =


(f) Use the t distribution table in Appendix B to determine the critical value of t for a two-tailed test at the 0.01 level of significance. (Use 3 decimal places.)

t-critical = ±


(g) Calculate the Means for each group:

M1 =
M2 =


(h) Calculate the Sum of Squares (SS) for each group: (Use 3 decimal places.)

SS1 =
SS2 =


(i) Calculate the Pooled Variance: (Use 3 decimal places.)

SP2 =


(j) Calculate the Standard Error of the Difference in the Means: (Use 3 decimal places.)

S(M1-M2) =


(k) Calculate the t statistic: (Use 3 decimal places.)

t =

(l) What decision should be made about the null hypopthesis (Ho)?

Fail to reject the null hypothesis, there is not a significant difference between the placebo and medication groups.

Reject the null hypothesis, there is not a significant difference between the placebo and medication groups.   

Reject the null hypothesis, there is a significant difference between the placebo and medication groups.

Fail to reject the null hypothesis, there is a significant difference between the placebo and medication groups.


(m) Calculate the estimated Cohen's d and r2 to measure effect size for this study. (Use 3 decimal places.)

d =
r2 =

(n) How would the results be presented in the literature?

The participants taking the pain medication reported less pain (M = 5.25, SD = 1.500) than the participants taking the placebo (M = 7.25, SD = 1.258). This difference was significant, t(7) = -2.043, p < 0.01.

The participants taking the pain medication reported less pain (M = 5.25, SD = 1.500) than the participants taking the placebo (M = 7.25, SD = 1.258). This difference was not significant, t(7) = -2.043, p > 0.01.  

  The participants taking the pain medication reported less pain (M = 5.25, SD = 1.500) than the participants taking the placebo (M = 7.25, SD = 1.258). This difference was not significant, t(6) = -2.043, p > 0.01.

The participants taking the pain medication reported less pain (M = 5.25, SD = 1.500) than the participants taking the placebo (M = 7.25, SD = 1.258). This difference was significant, t(6) = -2.043, p < 0.01.

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