Module 9, Checkpoint 1 PDF

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Checkpoint 1 from Module 9 of OLI...

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Module 9, Checkpoint 1 Sunday, November 3, 2019

10:49

1. The owner of a test prep company was interested in whether students who took the company's face to face test prep class did better on the GRE (a standardized test required for admission to many graduate programs) than students who followed the test prep company's live online program. The live online test prep class met in an online classroom with live video instruction for the same number of hours as the face to face class. In which situation could the test prep company use the two-sample t-test for comparing two population means? A. The test prep company gives each student a pretest. Then each student completes the live online test prep class. Afterwards, each student takes a posttest. The test prep company wants to compare the pretest and posttest GRE scores for each student to see whether the data will show an improvement. B. The test prep company randomly divides the students into two groups. One of the groups receives the face to face test prep class and the other group receives the live online test prep class. After completing their test prep course, each student takes the GRE and the test prep company compares the test scores of the two groups. C. The students take part of their GRE test prep course online and the remaining part in the face to face method. The test prep company asks the students which they liked better. The company wants to determine if the majority prefer the online class. B. The test prep company randomly divides the students into two groups. One of the groups receives the face to face test prep class and the other group receives the live online test prep class. After completing their test prep course, each student takes the GRE and the test prep company compares the test scores of the two groups.

2. In a study of the impact of smoking on birth weight, researchers analyze birth weights (in grams) for babies born to 189 women who gave birth in 1989 at a hospital in Massachusetts. In the group, 74 of the women were categorized as "smokers" and 115 as "nonsmokers." The difference in the two sample mean birth weights (nonsmokers minus smokers) is 281.7 grams and the 95% confidence interval is (76.5, 486.9) Which gives the best interpretation of what we can conclude about the impact of smoking on birth weight? A. We are 95% confident that on average, smoking causes lower birth weights of between 76.5 grams to 486.9 grams. B. There is a 95% chance that if a woman smokes during pregnancy her baby will weigh between 76.5 grams to 486.9 grams less than if she did not smoke. C. When smokers are compared to nonsmokers, we are 95% confident that the mean weight of babies of nonsmokers is between 76.5 grams to 486.9 grams more than the mean weight of babies of smokers. D. This study does not suggest that there is a difference in mean birth weights when we compare smokers to nonsmokers. C. When smokers are compared to nonsmokers, we are 95% confident that the mean weight of babies of nonsmokers is between 76.5 grams to 486.9 grams more than the mean weight of babies of smokers.

3. Breastfeeding burns up to 500 calories per day, so does that mean that women who breastfeed their infants will lose more weight than women who formula feed

their infants? A group of researchers studied the amount of weight lost after giving birth by mothers who breastfed their infants and mothers who chose formula feeding. They randomly chose 29 breastfeeding mothers and 21 formula feeding mothers. The researchers recorded how much weight each group lost at 12 months after childbirth. The amount of weight lost was found to be normally distributed. The difference in the mean amount of weight lost for the two samples (breastfeeding vs. formula feeding) is 2.0 kg and the 95% confidence interval is (1.05, 4.19). Which statement gives the best interpretation of what we can conclude about the impact of breastfeeding on the amount of weight lost after childbirth? A. We are 95% confident that on average, breastfeeding causes an extra weight loss of 1.05 kg to 4.19 kg. B. There is a 95% chance that if a woman breastfeeds her baby that she will lose an extra 1.05 kg to 4.19 kg than if she used formula to feed her baby. C. When breastfeeding mothers are compared to formula feeding mothers, we are 95% confident that the mean amount of weight lost 12 months after childbirth is between 1.05 kg and 4.19kg more than the mean amount of weight lost by formula feeding mothers. D. This study does not suggest that there is a difference in mean amount of weight lost after childbirth when we compare breastfeeding mothers to formula feeding mothers. C. When breastfeeding mothers are compared to formula feeding mothers, we are 95% confident that the mean amount of weight lost 12 months after childbirth is between 1.05 kg and 4.19kg more than the mean amount of weight lost by formula feeding mothers.

4. Do oddsmakers believe that teams who play at home will have home field advantage? Specifically, do oddsmakers give higher point spreads when the favored team plays home games as compared to when the favored team plays away games? Two samples were randomly selected from three complete National Football League seasons (1989, 1990, and 1991). The first sample consisted of 50 games, where the favored team played in a home game, while the second sample consisted of 50 games, where the favored team played in an away game. The oddsmakers' point spreads (which are the number of points by which the favored team is predicted to beat the weaker team) were then collected. If μ 1 and μ 2 represent the mean point spread for home games and away games, respectively, what is the appropriate pair of hypotheses in this case?

H0:μ1=μ2 Ha:μ1>μ2 5. Do college students who are in a fraternity or sorority attend more parties than college students who are not affiliated with a fraternity or sorority? A statistics class randomly selected 50 students who were in a fraternity or sorority and 50 students who were not affiliated with a fraternity or sorority and asked them to report how many parties they had attended in the past month. If μ1 and μ2 represent the number of parties attended by the fraternity and sorority members (μ1) and the unaffiliated students (μ2), respectively, what is the appropriate pair of hypotheses in this case?

H0:μ1=μ2 Ha:μ1>μ2

6. You are analyzing data for a research project. You have a two-sided two-sample t-test with the following hypotheses being tested: H0:μ1−μ2=0 Ha:μ1−μ2≠0 Which of the following results for the confidence interval does not provide enough evidence to reject the null hypothesis? A. 95% confidence interval: (−4.223, −1.989) B. 95% confidence interval: (−2.945, 0.983) B. 95% confidence interval: (−2.945, 0.983)

7. You are analyzing data for a research project. You have a two-sided two-sample t-test with the following hypotheses being tested: H0:μ1−μ2=0 Ha:μ1−μ2≠0 Which of the following results for the confidence interval provides enough evidence to reject the null hypothesis? A. 95% confidence interval: (−3.853, −0.943) B. 95% confidence interval: (−0.285, 1.345) A. 95% confidence interval: (−3.853, −0.943)

8. A teacher is experimenting with a new computer-based instruction and conducts a study to test its effectiveness. In which situation could the teacher use a hypothesis test for matched pairs? A. The teacher gives each student in the class a pretest. Then she teaches a lesson using a computer program. Afterwards, she gives each student a post-test. The teacher wants to see if the difference in scores will show an improvement. B. The teacher randomly divides the class into two groups. One of the groups receives computerbased instruction. The other group receives traditional instruction without computers. After instruction, each student takes a test and the teacher wants to compare the performance of the two groups. C. The teacher uses a combination of traditional methods and computer-based instruction. She asks students which they liked better. She wants to determine if the majority prefer the computer-based instruction. B. The teacher randomly divides the class into two groups. One of the groups receives computerbased instruction. The other group receives traditional instruction without computers. After instruction, each student takes a test and the teacher wants to compare the performance of the two groups. 9. A researcher wants to determine whether shoppers will spend more money at the grocery when they use a credit card to pay for their groceries rather than cash. In which situation could the researcher use a hypothesis test for matched pairs? A. The people in the experiment are told to use only cash for their grocery shopping for one trip and report how much money they spent. The next trip, the same people in the sample use only credit cards for their grocery shopping and calculate the total. The researcher compares the total spent by each individual to see if they spent more, on average, when using cash or the credit card. B. The researcher randomly assigns half of the sample to only use cash for their grocery shopping for one trip to the grocery store. The other half of the sample uses only credit cards. The

researcher compares the amount of money spent by each of the two groups. C. The researcher asks the people in the sample whether they prefer to shop for their groceries using a credit card more than with cash (yes/no). A. The people in the experiment are told to use only cash for their grocery shopping for one trip and report how much money they spent. The next trip, the same people in the sample use only credit cards for their grocery shopping and calculate the total. The researcher compares the total spent by each individual to see if they spent more, on average, when using cash or the credit card.

10. Some research suggests that first born children may have higher IQ scores than their later born siblings. Do first-born identical twins have higher IQ scores than their second-born sibling? Data from a 1998 study were analyzed to determine whether first-born identical twins have higher IQ scores than their second-born siblings. Ten pairs of adult identical twins were assessed and their Full Scale IQ scores were calculated. Let μ 1 and μ 2 represent the mean Full Scale IQ score for all first-born identical twins and secondborn identical twins, respectively, and let μ d be the mean of the differences in IQ score of all identical twins (IQ score of first-born twin minus IQ score of second-born twin).

What is the appropriate null and alternative hypotheses?

H0:μd=0 Ha:μd>0 11. The director of a daycare center noticed that the infants were getting more diaper rashes than usual in the summer time. The policy of the center was to change the diapers on a schedule every three hours. The director wanted to find out if adjusting the diaper-changing schedule to every two hours would significantly reduce the number of diaper rashes. Since some of the infants seemed to have more sensitive skin, she decided to directly compare the number of diaper rashes for each individual infant when the diaper was changed every three hours versus every two hours. For the first week, the daycare center changed the diapers as usual every three hours and noted the number of days that each infant had symptoms of a diaper rash. During the second week, the teachers changed diapers every two hours and recorded the number of days with symptoms of a diaper rash. At the end of the two weeks, they compared for each individual infant the number of days with symptoms of a diaper rash when the diapers were changed every three hours versus every two hours. Let μ 1 and μ 2 represent the mean number of days with symptoms of a diaper rash when diapers were changed every three hours and two hours, respectively, and let μ d be the mean of the differences in thenumber of days with symptoms of a diaper rash (diaper rash days when changed every three hours minus diaper rash days when changed every two hours). What is the appropriate null and alternative hypotheses? H0:μd=0 Ha:μd>0

12. Research suggests that the pressure of being timed may interfere with performance on tests that involve mathematical problems. A fictional study was conducted with 30 sixth graders. First, the sixth graders were given a math test that contained 50 problems and were told that they had only one hour to complete it (timed condition). The same sixth graders were later given a math test that contained 50 problems and were told that they could have as much time, as needed, to

complete the test (unlimited time condition). The total number of correct answers for each sixth grader was then calculated for each condition. Then, for each student, the difference between the two scores (timed − untimed) was calculated. The researchers hypothesized that the sixth graders would get fewer correct answers when they took the test with a time limit than when they had unlimited time. If μ 1 and μ 2 represent the number of correct answers during the timed condition and the unlimited time condition, respectively, and let μ d be the mean of the differences in the number of correct answers (timed − untimed) of all sixth graders. What is the appropriate null and alternative hypotheses? H0:μd=0 Ha:μd 0 C. H_o: μ1 - μ2 = 0 H_a: μ1 - μ2 > 0

20. A researcher wants to investigate the attitude level of different cows in the Midwest region of the

United States. He randomly selects 100 farmers from 10 counties in the region and gives them a survey on whether their cows have bad attitudes or good attitudes. The farmers then attend a workshop on attitude determination in cows. The same 100 farmers are then given a follow up survey to reassess the attitudes of their cows. The surveys are then compared to each other to see if the workshop makes a difference in determination. Is this an example of an independent or paired sample? Independent

21. What is the non-parametric alternative to one-way between groups ANOVA with post-hoc tests? Kruskal-Wallis Test

22. For a t-test you need two variables: an IV that is ___________ and a DV that is ____________. Dichotomous; continuous

23. Given a 95% confidence interval for a t-test of (-2.3,2.3) what can we conclude bout whether the test is significant?

Not significant

24. As the n increases for the t-distribution it becomes more and more like a ________ distribution. A. Poisson B. Bernoulli C. normal D. binomial C. normal

25. ______ are used when you only have two groups or two time points. t-tests

26. ______ techniques are used when you have two or more groups or time points

ANOVA 27. ________ techniques are used when you test the same people on more than one occasion, or you have matched pairs Paired-samples/repeated measures

28. ________ techniques are used when the participants in each group are different people or independent Between-groups/independent samples 29. _____ is used when you have only one independent variable. One-way ANOVA

30. ______ is used when you have two independent variables Two-way ANOVA

31. ______ is used when you need to control for an additional variable that may be influencing the relationship between your independent and dependent variable ANCOVA (covariance)

32. ____ is the strength of the difference between groups, or the influence of the independent variable Effect size

33. _______ effect size statistics indicate the proportion of variance of the dependent variable that is explained by the independent variable. Partial eta squared

34. _____ presents difference between groups in terms of standard deviation units. Cohens d

35. What is the non-parametric alternative to the independent samples t-test? Mann-Whitney U test

36. What is the non-parametric alternative to paired samples t-test? Wilcoxon Signed Rank Test

37. What is the non-parametric alternative to one-way repeated measures ANOVA? Friedman test

38. In the case of C →Q, our __________ variable X is categorical.

explanatory

39. Samples are __________ when each observation in one sample is matched with an observation in the other sample. Dependent

40. In the case of C → Q, our response variable __________ is quantitative. Y

41. A two-sample t-test looks at the effect of a two-valued __________ explanatory variable on a quantitative response variable. categorical

42. When comparing __________ independent sample means, we use a __________-sample t-test. two

43. A __________ t-test looks at the effect of a two-valued categorical explanatory variable on a quantitative response variable. Two-sample

44. When comparing __________ pairs from dependent samples, we conduct a paired t-test. matched...