+1 862 207 3288 Problems 7, 21, 25
7. Recall that the file Baseball Salaries 2011 Extra.xlsx contains data on 843 major league baseball players during the 2011 season. Use StatTools to find the mean, median, standard deviation, and first and third quartiles of Salary, broken down by each of the following categories, Comment on your findings.
a. Team
b. Division
c. Whether they played for the Yankees
d. Whether they were in the playoffs
21. The file P02_07xsx includes data on 204 employees at the (fictional) company Beta Technologies.
a. Create a table of correlations between the variables Age, Prior Experience, Beta Experience, Education, and Annual Salary, which of the first four of these variables is most highly correlated (in a positive direction) with Annual Salary?
B. Create scatterplots of Annual Salary, (Y axis) versus each of Age, Prior Experience, Beta Experience, and Education.
c. For the variable from part a most highly correlated with Annual Salary, create a linear trend line in its scatterplot with the corresponding equation shown in the chart. What does this equation imply about the relationship between two variables?
25.The file P02_39.xlsx lists the average high school student scores on the SAT exam by state. There are three components of the SAT: critical reading, math, and writing. These components are listed, along with their sum. The percentahe of all potential students who took the SAT is also listed by state. Create correlations and scatterplots to explore the following relationships and comment on the results.
a. The relationship between the combined score and the percentage taking the exam
b. The relationship between the critical reading and writing components.
c. The relationship between a combined verbal component (the average of critical reading and writing) and the math component.
d. The relationship between each of critical reading, math, and writing with the combined score. Are these bound to be highly correlated because the sum of the three components equals the combined score?
Conceptual Questions
C.1. When you are trying to discover whether there is a relationship between two categorical variables, why is it useful to transform the3 counts in a crosstabs to percentages of row or column totals? Once you do this, how can you tell if the variables are related?
C.2. Suppose you have a crosstabs of two “Yes/No’ categorical variables, with the counts shown as percentage of row totals. What will these percentages look like if there is absolutely no relationship between the variable? Besides this cases, list all possible types of relationships that could occur. (There aren’t many).
C.10. In checking whether several times series, such as monthly exchange rates of various currencies, move together, why do most analysts look at correlations between their differences rather than correlations between the original series?
Discussion Board
Understanding statistical inferencing and population sampling is important. Suuppose that you want to know the opinions of American school teachers about establishing a national test for high school graduation. You obtain a list of the members of the National Education Association and mail a questionnaire to 3, 000 teachers chosen at random from this list. IN all 823 teachers return the questionnaire. Identify the relevant populations. Do you believe there is a good possibility of non-sampling error? Why or Why not? Be sure to support your response with information from your textbook.
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