# Lesson 11: A researcher conducts an experiment comparing two treatment conditions and obtains data with 10 scores for each treatment condition

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1. A researcher conducts an experiment comparing two treatment conditions and obtains data with 10 scores for each treatment condition. a. If the researcher used an independent-measures design, how many subjects participated in the experiment? b. If the researcher used a repeated-measures design, how many subjects participated in the experiment? c. If the researcher used a matched-subjects design, how many subjects participated in the experiment? 2. A sample of difference scores (D values) from a repeated-measures experiment has a mean of MD = 5.00 with a variance of s2 = 16. a. If n = 4, is this sample sufficient to reject the null hypothesis using a two-tailed test with α = .05? b. Would you reject H0 if n = 16? Again, assume a two-tailed test with α = .05. 3. A researcher studies the effect of cognitive psychotherapy on positive self-regard. The number of positive statements made about oneself is recorded for each participant during the first meeting. After 8 weekly therapy sessions, the measures are repeated for each person. For the following data, a. Calculate the difference scores and MD. b. Compute SS, sample variance, and estimated standard error. c. Is there a significant treatment effect? Use α = .05, two tails. ____________________________________________ Before After ____Participant______treatment________treatment__ A 7 10 B 6 13 C 9 12 D 5 8 ____________________________________________