Effect-Size Statistics What are Cohen's d and the confidence interval of the difference? The confidence interval is listed in the SPSS output. You can do a quick internet search for "Cohen's d" calculator and find many websites that will allow you to quickly perform that calculation. Once you have your effect sizes, interpret them. Talk about what they mean. HINT: Part of your interpretation should address whether these statistics are consistent with your conclusion to reject/accept in the hypothesis test. We test the following hypothesis, 1. Ho: Md = 0 i.e. The cats have equal preference for ald and new brand of cat fo 2. H: Hd #0 i.e. The cats do not have equal preference for old and new brand Where Hd represents population mean difference between new and old brands. Hd = new - Hold 3. Here, level of significance = a = 0.05 4. Reject Ho if, | Observed t| > Critical t Where, Critical t = ta/2,n-1 = to.05/2,6-1 = to.025,5 = 2.571 Hence, reject Ho if lobserved t| > 2.571 5.Table showing calculations : 5.Table showing calculations: Old brand 33 30 32 29 30 25 Total Here, New brand 32 40 36 37 37 36 di-New-old -1 10 4 8 7 11 39 Here, Sd= - di = 6.5 = t= n (di a) - = 3.61 V d = difference The value of the test statistic is given by, n* Id Sd = 4.4159 6. a. Here, after calculating t observed = 3.61, we compare it with t critical. b. Based on the rejection criterion we see that lobserved t| > 2.571 c. Hence, we reject the null hypothesis. d. At 5% level of significance we have enough evidence to conclude that the cats do not have equal preference for old and new brand of cat food.