Question

A psychologist is interested in whether the number of times a day schizophrenics hear voices is impacted by the drug Clozapine, an antipsychotic. The researcher studies how many voices schizophrenics perceive in a 2 hour period between a group of participants who have taken Clozapine and a group of participants who take a placebo. The numbers are presented in the table below. Group 1 Placebo Group 2 Clozapine 9 4 8 5 4 6 7 5 5 3 7 Mean SS 10 2.8 a. State your null hypothesis in both symbols and words: b. State your alternative hypothesis in symbols and words: Calculate the appropriate statistic to determine if there were group differences. Conduct a two-tailed test with an alpha level of 0.05. d. What is the critical value you should use to determine if the test was significant? e. Should you reject or fail to reject your null hypothesis? f. What does that mean? Was there an effect of the drug or not? & Calculate Cohen's d as a measure of effect size. Is the effect considered small, medium, or large?

Answer 1

5,- SS (7,25 obsesuladi 5-1 solution : Given Mean 1091 group-1 is 7,= 7 Mean 6091 group-2 is 72 = 4.2 Standard deviation tosi group-1 is => Si = /10 ni => S, - 1.58 Standard deviation 404 quoup-2 is , S2 ss > S2 껐 S2 = 0.84 @ Null hypothesis ; → There is no difference between mean of group of participants who have taken Clozapine (meain 42) and a group of participants who takes a placebo i Mean ele). M2 12,8 5-1 (12=5 observatie => Se Symbol i+ Ho ó lle = o alternative hypothesis : -> There is a difference between mean of group of participants who have taken Clozapine and a group of participants who takes a placebo Symbol :~ Ha i lle #42. © We test (please . mefer theory of t-test fou two population mean Fosa better understanding) 7 - Xe 171,-1) s*+(12-1) 5 use t 0 t 2 (+) 7,+ m2 -2 -4.2 => ta 5+5-2 775- (5-1) (1.58)*+(5-1) (0.84) 754) => t = 3.499 (using calculator we calculate it). és t statistic = 3,499

at a: 0,05 or to 00 hypothesis. a) Now, we find critical value ta using t- table. tc = 2.306 for rejecting null hypothesis for this two tailed test. R={titl>te = 2.306} t = 3,499 > tc = 2,306 co It is concluded that the null hypothesis is rejected. @ we reject null It means that alternative hypothesis is true So, There is difference between population population mean of group-1 and There is an effect of the daug exist. Noco. We meas wie Cohen's d meassure of effect size using beloco formula Cohen's d (x2-x) 5, ²+52 (6.55)60.84) >> Cohen's d = 2.212903 os effect size is high of effect size is large. gaoup-2, => Cohen's d = 164,2-7) 2 2. 2

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