Question

21.27 Mood and food. In a study of the effects of mood on evaluation of nutritious food, 208 subjects were ran- domly assigned to read either a happy story (to induce a positive mood) or a control (no story, neutral mood) group. Subjects were then asked to evaluate their atti- tude toward a certain indulgent food on a nine-point scale, with higher numbers indicating a more positive attitude toward the food. The following table summa- rizes data on the attitude rating:14 Group Positive mood Neutral mood n 104 104 ħ 4.30 5.50 s 2.05 1.74 (a) What are the standard errors of the sample means of the two groups? (b) What degrees of freedom does the conservative Op- tion 2 use for two-sample t procedures for these data? (c) Test the null hypothesis of no difference between the two group means against the two-sided alterna- tive. Use the degrees of freedom from part (b).

Answer 1

solution: 1. a) Here we have to find standard coor Standard Coror (se): sel to the where Sp: J M.-) si +(12-1) 57 nith, 2 from the given Group | Positive mood heutral mood data we have n L F 104 L 4,30 2.05 1.74 lok 5.50 sp = ) (104-1)(2.059+(104-) (1.7401 104 1104-2 744.7003 206 = 3.61505 sp = 1.9018 Now, Standard error (se) = 1,9013. tout tou 2 1.9013 (0.138675049) SE = 0.26366287 we have to find df. df = nith -2 b) Here

did = cou & 104.2 dit = 206 c) from data the given Ho: Mi = M2 Hi! Mi M2 (two side: test) test stah'sdic SB table from the given to 4.30-5:50 0.26366287 t2-416513 P-valve - Ox00000916 < < (oros) we resect Ho at s%