A researcher is evaluating the changes in children’s self-regulation that occur during a six-week training program. Participants are observed at the beginning and at the end of the program and the researcher rates each individual’s level of performance. When the researcher’s standards for rating performance change from the first observation to the last, then the internal validity of the study is threatened by …. A. Statistical regression B. Maturation C. Instrumentation D. History

Aspirin III: Decision and Conclusion Regarding the experiment in the data frame Aspirin from the abd package, the researchers wanted to know whether or not taking aspirin affects one's risk of developing cancer. Recall that they defined their parameters as follows: p1 = the proportion of ALL individuals who would develop cancer, if all of them were to take aspirin like the subjects in the Aspirin group did. p2 = the proportion of ALL individuals who would develop cancer, if all of them were to take a placebo, like the subjects in the placebo group did. They ran the code for a two-sided significance test and got the following results: ## ## ## Inferential Procedures for the Difference of Two Proportions p1-p2:##   cancer grouped by treatment ## ## ## Descriptive Results:## ##          yes     n estimated.prop## Aspirin 1438 19934        0.07214## Placebo 1427 19942        0.07156## ## ## Inferential Results:## ## Estimate of p1-p2:    0.0005805 ## SE(p1.hat - p2.hat):  0.002586 ## ##…

Bullying,” according to noted expert Dan Olweus, “poisons the educational environment and affects the learning of every child.” Bullying and victimization are evident as early as preschool, with the problem peaking in middle school. Suppose you are interested in the emotional well-being of not only the victims but also bystanders, bullies, and those who bully but who are also victims (bully-victims). You decide to measure anxiety in a group of bullies and a group of victims using an 18-item, 5-point anxiety scale. Assume scores on the anxiety scale are normally distributed and that the variances of the anxiety scores are the same among bullies and victims. The group of 23 bullies scored an average of 40.1 with a sample standard deviation of 10 on the anxiety scale. The group of 28 victims scored an average of 46.8 with a sample standard deviation of 11 on the same scale. You do not have any presupposed assumptions about whether bullies or victims will be more anxious, so you formulate…

An economist wonders if corporate productivity in some countries is more volatile than in other countries. One measure of a company's productivity is annual percentage yield based on total company assets.A random sample of leading companies in France gave the following percentage yields based on assets. 4.6 5.4 3.4 3.1 2.4 3.5 2.8 4.4 5.7 3.4 4.1 6.8 2.9 3.2 7.2 6.5 5.0 3.3 2.8 2.5 4.5 Use a calculator to verify that the sample variance is s2 ≈ 2.109 for this sample of French companies.Another random sample of leading companies in Germany gave the following percentage yields based on assets. 3.3 3.2 3.2 4.1 5.4 5.5 5.0 5.4 3.2 3.5 3.7 2.6 2.8 3.0 3.0 2.2 4.7 3.2 Use a calculator to verify that s2 ≈ 1.077 for this sample of German companies.Test the claim that there is a difference (either way) in the population variance of percentage yields for leading companies in France and Germany. Use a 5% level of significance. How could your test conclusion relate to the…