HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 144

Hypothesis test: T-Test µ1 -µ2 A farmer compared the 15-day mean weight of two sets of chicks, one group receiving feed supplement A and the other supplement C. Twenty two chicks only one day old were assigned randomly to the two groups. To distinguish between the two groups of eleven, which were caged together to minimize other influences, the heads of the chicks were stained red and purple respectively with a harmless vegetable dye. The individual weights were recorded in the table below. From the means at the end of the table it appears that supplement A produces a higher mean weight. Weights x σ X Supp. A 57 120 101 137 119 117 104 73 53 68 118 97 27.75 Supp. C 89 30 82 50 39 22 57 32 96 31 88 56 26.54 The farmer wishes to know, at the 1% test level, whether this is statistically significant. Our hypotheses are: H0: The effects are the same (µ1 = µ2 ) ie. There is no effect from the supplement. HA: Supplement A is better (µ1 > µ2 ) Enter the data into columns C1 and C2 of the Statistics aplet. We are dealing with two independent samples in this case and so we need to choose from those tests which involve two samples. Since we know the standard deviations of only these samples, we must again use a Student-t test. We then change to the NUM SETUP view to import the summary statistics. The import screen can be seen on the right. The results of the importation can be seen right. Since the two standard deviations for the samples are similar, and the sample sizes are the same, a more accurate estimate of the population standard deviation will be obtained if the data is pooled, so ensure that this option is ed. 144