12.1 What is measured by the estimated standard error that is used for the independent measures t statistic? 12.2 One sample has n = 15 with SS = 1570, and a second sample has n = 15 with SS = 1650. a. Find the pooled variance for the two samples. b. Compute the estimated standard error for the sample mean differences (i.e. for the two groups). c. If the sample mean difference (i.e. M1 - M2) is 8 points, is this enough to indicate a significant difference for a two-tailed test at = .05 level? d. If the sample mean difference (i.e. M1 - M2) is 12 points, is this enough to indicate a significant difference for a two-tailed test at = .05 level? 12.3 Siegel (1990) found that elderly people who owned dogs were less likely to pay visits to their doctors after upsetting events than were those who did not own pets. Similarly, consider the following hypothetical data. A sample of elderly dog owners is compared to a similar group (in terms of age and health) who do not own dogs. The researcher records the number of visits to the doctor during the past year for each person. The data are as follows: Control Group Dog Owners 11 5 8 4 6 7 7 4 10 8 6 9 a. Is there a significant difference in the number of doctor visits between dog owners and control subjects? Use a two-tailed test with = .05. (Note) for problems 12.2 & 12.3 above: Be sure and show a full diagram of the research design. Also show all steps and calculations you made for each test following the process outlined in the t-test formula sheet handout. What statistical decision do you make in each case