Do bonds reduce the overall risk of an investment portfolio? Let x be a random variable representing annual percent return for Vanguard Total Stock Index (all stocks). Let y be a random variable representing annual return for Vanguard Balanced Index (60% stock and 40% bond). For the past several years, we have the following data. x: 21 0 12 11 31 21 11 −14 −17 −8 y: 8 −2 26 14 15 21 13 −2 −2 −2   (a) Compute Σx, Σx2, Σy, Σy2. Σx   Σx2   Σy   Σy2   (b) Use the results of part (a) to compute the sample mean, variance, and standard deviation for x and for y. (Round your answers to four decimal places.)   x y x     s2     s     (c) Compute a 75% Chebyshev interval around the mean for x values and also for y values. (Round your answers to two decimal places.)   x y Lower Limit     Upper Limit

In the book Business Research Methods (5th ed.). Donald R. Cooper and C. William Emory discuss studying the relationship between on-the-job accidents and smoking. Cooper and Emory describe the study as follows: Suppose a manager implementing a smoke-free workplace policy is interested in whether smoking affects worker accidents. Since the company has complete reports of on-the-job accidents, she draws a sample of names of workers who were involved in accidents during the last year. A similar sample from among workers who had no reported accidents in the last year is drawn. She interviews members of both groups to determine if they are smokers or not. The sample results are given in the following table. On-the-Job No 7 Smoker Heavy Moderate Nonsmoker 16 Column total 34 Heavy Moderate Yes Nonsmoker Total 12 6 Expected counts are below observed counts No Accident Total 19 7 9.21 9 Row 1 Row 2 Row 3 Column 1 Column 2 16 32 Accident 12 9.79 6 Accident Row Total 7.27 16 15.52 32 7.73 16…

Reading is fundamental to a teenager's ability to perform well in school. Assume a researcher is interested in the ability of the number of books read over the summer to predict ACT Reading scores. Using a random sample of 10 random high school students the researchers recorded the number of books read over the summer and the students' ACT Reading scores. Books Read (X) ACT Score (Y) (X- Xmean) (Y - Ymean) (X-Xmean)(Y-Ymean) (X-Xmean)? (Y - Ymean)? 2 16 -5.4 -14.9 81 29 221 2 19 -5.4 -11.9 64 29 141 3 17 -4.4 -13.9 61 20 192 4 25 -3.4 -5.9 20 12 34 21 -3.4 -9.9 34 12 97 24 -1.4 -6.9 10 2 47 6 21 -1.4 -9.9 14 2 97 8 24 0.6 -6.9 -4 47 7 27 -0.4 -3.9 2 15 10 22 2.6 -8.9 -23 7 78 Total 52 216 259.1 113.3 969.3 МEAN 7.4 30.9 a. Identify the regression line using the number of books read to predict ACT Reading score. Use a = .05 to evaluate the quality of the prediction of the regression line. b. What is the predicted ACT Reading score when 5 books are read?

Three components are randomly sampled, one at a time, from a large lot. As each component is selected, it is tested. If it passes the test, a success (S) occurs; if it fails the test, a failure (F) occurs. Assume that 82.0% of the components in the lot will succeed in passing the test. Let X represent the number of successes among the three sampled components. Find P(X= 3). (Round the final answer to three decimal places.)

18 A sample of n=8 scores has a mean of M=12. One new score is added to the sample and the new mean is found to be M=13. What is the value of the new score?

A psychologist found a study which claiming that 32% of patients who visit a psychologist have symptoms of anxiety. This psychologist had 44 patients visit. Let x = the number of patients that had symptoms of anxiety. (a) The random variable is which of the following? O the number of psychologists O the number of patients who visited the psychologist the number of patients who had symptoms of anxiety O the number of patients without symptoms of anxiety (b) How many total patients did the psychologist have visit?

Find the variance(2 decimal).

A psychologist would like to examine the effects of a new drug on the activity level of animals. Three samples of rats are selected with n=5 in each sample. One group gets no drug, one group gets s small dose, and the third group gets a large dose. The psychologist records the activity level for each animal. The data from this experiment are presented below.   No drug Small dose Large dose 5, 3 , 1 , 1 , 5 5, 5, 9, 6, 5 10, 12, 9, 6, 8 =3, SS=16 =6, SS=12 =9, SS=20   Do these data indicate any significant differences among the three groups? Test with α=0.05.                        Compute the effect size and interpret the result.

Which of the following is a true statement? A. The expected value is the most frequently occurring value of the random variable. B. Variance is always >=0 C. Variance can be negative D. F(x)=P(X=x)

man loves, as everyone should, to collect and analyze statistical information. He wishes to find a relationship between how many hours students study and how they do on their statistics tests.  He takes a random sample of 16 students at Ideal U., asks how many hours they studied for a university-wide stat test and how they did on the test, enters the data into a computer for analysis and presents the results below.   ANALYSIS OF HOURS AND GRADES (n = 16):   Descriptive Statistics:   HOURS GRADES Mean:  4.2  75.8 Mode:  5.0  79.0 St. Dev:  2.3  10.1   Quartiles: Q0  2.0  34.0 Q1  3.2  53.7 Q2  4.7  78.5 Q3  6.3  86.9 Q4  9.0  97.0   Regression Analysis: Reg. Eq. is: GRADE = 16.9 + 9.025*HOURS Rsquared = .985 std error = 0.027   F = 8.52 p = .018     What problem might there be in using the regression model to predict what grade a student might get if they studied 10 hours?         a. The predicted grade for 10 hours is more than 100, which is impossible.   b. The value of 10…