Two-Sample Study (tap-only and bottle-only)

a.Provide the null and research hypotheses (defining all symbols) for comparing the mean weight gain in the two water groups.

b.Use a statistical test to determine whether the variances of the two groups (tap-only and bottle-only) are different.

c.Based on the response to part (b), perform the appropriate two-sample t-test (equal or unequal variances). Interpret the results.

d.Based on the response to part (b), provide an interval estimate for the mean difference in weight gain between the two groups. Interpret

3b,c,d The TTEST Procedure Variable: wtgain Distribution of wtgain 30 - 20 - Percent 10 - 20 2 15 Percent 10 1 - OO OF OC group O 20 30 40 50 60 70 wtgain - Normal Kernel Q-Q Plots of wtgain 7 O 55 2 60 50 50 45 - wtgain wtgain 40 40 - 30 35 O 20 - BO O -3 -2 -1 0 2 3 -3 -2 -1 0 2 3 Quantile Quantile3b,c,d The TTEST Procedure Variable: wtgain group Method N Mean Std Dev Std Err Minimum Maximum 40.0107 5.7299 24.5000 63.9000 1 270 0.3487 2 315 42. 1048 4. 1538 0.2340 30.0000 51.7000 Diff (1-2) Pooled 2.0940 4.9439 0.4100 Diff (1-2) Satterthwaite -2.0940 0.4200 95% group Method Mean 95% CL Mean Std Dev CL Std Dev 1 40.0107 39.3242 40.6973 5.7299 5.2840 6.2588 2 42. 1048 41.6443 42.5652 4. 1538 3.8528 4.5062 Diff (1-2) Pooled -2.0940 -2.8993 -1.2887 4.9439 4.6757 5.2450 Diff (1-2) Satterthwaite -2.0940 -2.9192 -1.2688 Method Variances DF t Value Pr > It| Pooled Equal 583 -5.11 <.0001 satterthwaite unequal equality of variances method num df den ff value pr> F Folded F 269 314 1.90 <.0001>