Question

ation: A social psychologist gave a questionnaire assessing cóice i rkers to nine participants both before and after they attended a film about the importance of Study Description: A social psych farm wo union organization of farm workers indicating higher concern. . The results (data) are shown in the table below, with higher scores Using the .05 significance level and a two-tailed test, do these results support the hypothesis that the film affected participants' conce i rn for the lives of farm workers? (In other words, did participants noe in their concern for the lives of farm workers after vi

Answer 1

Null Hypothesis(H0):

Population mean difference (after - before) is not significantly different from 0. _d =0

Alternative Hypothesis(H1):

Population mean difference (after - before) is significantly different from 0. _d 0

Test statistic(t):

Sample mean difference, _d =3; Sample size, n =9

Sample std.deviation of differences, S_d = = =1.5

Test statistic, t =(_{d​​​​​​}​​​- _d)/(S_d/) =(3 - 0)/(1.5/​​​​​​) =6

Critical value of t(t_crit):

At 0.05 significance level and at n - 1 =8 degrees of freedom, the critical value of t for a two-tailed test is: t_crit =2.3

Since the test statistic (t =6) fell in the rejection region, we reject the null hypothesis(H0) at 0.05 significance level.

Thus, there is a strong evidence that the population mean difference is significantly different from 0.

(c) Effect size = _d/S_d =3/1.5 =2

(d) Since 2 > 0.8, the effect size is large, i.e., the difference can be observed easily from the given data.