Q1: Placebo effect of exercise In a high-profile research study, Crum and Langer (2007) performed an experiment to test whether the relationship between physical exercise and health is impacted by one's mindset: in other words, if there is any "placebo effect" of exercise. A sample of 84 randomly selected hotel workers in the United States were placed either into a treatment group (n=44) or control group (n=40) depending on which hotel they worked at. The treatment group was given information demonstrating how their work is good physical exercise, while the control group was not given this information. They measured the body mass index (BMI) for each worker before the experiment and again four weeks after the experiment. a. Are the treatment group and control group independent of each other, and if so why? b. Now consider the treatment group alone: are the measurements of BMI taken before and after the experiment independent of each other, and if so why? c. What is the most appropriate statistical test to determine whether the average BMI of the treatment group had changed after the information on exercise was given to the workers, and why? d. Using the usual mathematical notation, write an appropriate null and alternative hypothesis for the statistical test you identified in part 1c above. e. The researcher finds a mean difference in BMI for the treatment group (after minus before) of -0.35, and an associated test statistic of -3.10. What does the negative sign of the difference tell us about the relationship between information and BMI? f. The appropriate P-value is 0.007. What is the researcher's decision for the test at the 1% significance level?

A study compared tooth health and periodontal damage in a group of 40 young adult males with a tongue piercing and a control group of 50 young adult males without tongue piercing.  Here are the summary statistics: Group Sample size Mean of enamel cracks StDev of enamel cracks Tongue piercing 40 4.1 3.7 No Tongue piercing 50 1.3 1.6   One question of interest was whether individuals with tongue piercing had more enamel cracks, on average. Is there evidence at 1% level that young adult males with a tongue piercing have significantly more enamel cracks than young adult males without a tongue piercing?             Which method will you use to perform the test? Choose the correct one. 1-sample T test 2-sample T test 2-sample Z test. 2-proportion Z test            Which distribution will you use here? If you use t distribution, give the degree of freedom. If you use z or normal, give the mean and standard deviation.

Sigall and Ostrove (1975) did an experiment to assess whether the physical attractiveness of a defendant on trial for a crime had an effect on the severity of the sentence given in a mock jury trials. Each of the participants in this study was randomly assigned to one of the following three treatment groups; every participant received a package that described a burglary and gave background information about the accused person. The three treatment groups differed in the type of information that they were given about the accused person’s appearance. Members of Group 1 were showing a photo of an attractive person; members of Group 2 were shown a photograph of an unattractive person; members of Group 3 saw no photograph. Some of their results are described here. Each participant was asked to assign a sentence (in years) to the accused person; the researchers predicted that more attractive persons would receive shorter sentences. a)Prior to assessment of the outcome, the researchers did a…

A particular paper described a study of children who were underweight or normal weight at age 2. Children in the sample were classified according to the number of sweet drinks consumed per day and whether or not the child was overweight one year after the study began. Is there evidence of an association between whether or not children are overweight after one year and the number of sweet drinks consumed? Assume that it is reasonable to regard the sample of children in this study as representative of 2 to 3 years old children and then test the appropriate hypotheses using a .05 significance level. (Round your answer to two decimal places.) Number of Sweet Overweight? Drinks Consumed per Day Yes No 22 930 1 73 2071 2 56 1681 3 or More 102 3389 x2 = | P-value interval Op< 0.001 O 0.001 s p < 0.01 O 0.01 sp < 0.05 O 0.05 sp < 0.10 Op2 0.10 There is --Select--- v to conclude that there is an association between whether or not children are overweight after one year and the number of sweet…

Researchers investigate how the presence of cell phones influence the quality of human interaction.  Subjects are randomly selected from a population and divided into an experimental group that is asked to leave their phones in the front of the room and a control group that are not asked to leave their cell phones at the front of the room.  Subjects are left alone for 10 minutes and then asked to take a survey designed to measure quality of interactions they had with others in the experiment.  What statistical test is appropriate?

How would you find (a.) and (b.)?? As well as finding the test statistic and p-value?

The director of student services at Oxnard College is interested in whether women are just as likely to attend orientation as men before they begin their coursework. A random sample of freshmen at Oxnard College were asked what their gender is and whether they attended orientation. The results of the survey are shown below: Data for Gender vs. Orientation Attendance Women Men Yes 440 410 No 238 239 What can be conduded at the a - 0.10 level of significance? For this study, we should use z-test for a population proportion a. The null and alternative hypotheses would be: Ho: Select an answer v Select an answer v Select an answer v (please enter a decimal and note that p1 and ul represent the proportion and mean women and and u2 represent proportion and mean for men.) H: Select an answer v Select an answer v Select an answer v (Please enter a decimal) b. The test statistic ? v (please show your answer to 3 decimal places.) c. The p-value = (Please show your answer to 4 decimal places.) d.…

Acne is a common skin disease that affects most adolescents and can continue into adulthood. A study compared the effectiveness of three acne treatments and a placebo, all in gel form, applied twice daily for 12 weeks. The study's 517 teenage volunteers were randomly assigned to one of the four treatments. Success was assessed as clear or almost clear skin at the end of the 12 week period. The results of the study can be seen in the table below. Using the appropriate statistical test, determine if there is significant evidence that the four treatments perform differently. If so, how do they compare.

Results on seat belt usage from the 2003 Youth Risk Behavior Survey were published in a USA Snapshot on January 13, 2005. The following table outlines the results from the high school students who were surveyed in the state of Nebraska. They were asked whether or not they rarely or never wear seat belts when riding in someone else's car. Using ? = .05, does this sample present sufficient evidence to reject the hypothesis that gender is independent of seat belt usage?     Female     Male Rarely or never use seat belt 206 323 Uses seat belt 1220 1157 (a) Find the test statistic. (Give your answer correct to two decimal places.)(ii) Find the p-value. (Give your answer bounds exactly.) ______< p < ________

State the hypotheses for each of the three separate tests included in the two-factor ANOVA.