Practice Problems Chapter 9 *For all assignments, show y0ur work (no credit if you don't!), only use formulas/procedures from this course (again, no credit if you don't follow the steps from class), round to hundredths place, and submit les in the formats noted in the assignment instructors. 1. A sample of 19 specially-trained dogs run an agility course in 6.5 minutes with a standard deviation of 0.75 minutes. The average dog trained on the course makes it around the course in 7.3 minutes. Is there a difference between the specially-trained group and the rest of the population? Answer parts ad below based on this question. a. This is a one-sample t-test. How do we know? b. Use the four-steps of hypothesis testing and an alpha level of 0.05 to answer the question above. c. What is the effect size calculation? Is it small, medium, or large? [Calculate this, no matter your conclusion. Also note that you need a number, not just a designation of small, medium, or large to get credit.) d. Calculate a 99% confidence interval. [Note that the critical value might be different than it is for problem #1. You should recalculate it for each problem.) Based on that interval, what do you conclude about the difference between the population mean and the sample mean? 2. A group of 100 "supertasters" gave broccoli an average bitter score of 8.5 with a standard deviation of 1.4. The general population gives broccoli an average bitter score of 6.4. Do "supertasters" score broccoli as signicantly m bitter than the rest of the population? Answer parts a-d below based on this question. a. This is a one-sample ttest. How do we know? b. Use the four steps of hypothesis testing to come to a decision- Test with an alpha level of o = .05. c. What is the effect size for the outcome (calculate this no matter what your outcome from #6)? Is the effect size small, medium, or large? Note that you need a number to get credit. Simply writing small, medium, or large is not sufficient. d. Construct a 99% condence interval. Based on the condence interval, what would you conclude (is the population mean different from the sample mean, or not)? Remember that you might need to use a different critical value. LTo test the impact of intensive tutoring in a statistics class, an instructor compares scores on a test given at the beginning of the semester (before the tutoring) and at the end of the semester (after the tutoring). The data are below. Use these data to answer parts ad below. *Remember POSTTEST - PRETEST a. This is a paired-samples ttest. How do we know? b. Is there a significant change between participants' scores from pretest to posttest? To answer the question, use all four steps of hypothesis testing and an alpha level of .01. c. Find the effect size for the problem. Is it small, medium, or large? Calculate this, no matter the outcome of the hypothesis test. As in earlier problems, a numeric value is required for credit- d. Find the 95% condence interval. Based on the interval, is there a difference between pretest and posttest scores? (Remember to recalculate your critical value.) 4. A group of puppies are tested to see how well they perform in response to commands when they receive a food treat vs. when they receive praise. The data are below. Use these data to answer parts a-d below. Food Treat Verbal Praise 3 3 5 2 6 5 2 2 1 5 *For this case, it doesn't really matter which way that you subtract to find your difference scores a. This is a paired-samples t-test. How do we know? b. Is there a significant difference between scores based on reward type? To answer the question, use all four steps of hypothesis testing and an alpha level of .05. c. Find the effect size. Is it small, medium, or large? (Find this, no matter the outcome of the hypothesis test. Make sure you include a number for credit.) d. Find the 90% confidence interval. Based on the interval, is there a difference between pretest and posttest scores? (Remember to recalculate your critical value.)