Question 2 Explain briefly how the VIF of a regressor is related to the variance of estimated effect for that regressor. That is, explain how VIF(x;) is related to the variance of 3₁. Explain briefly why this shows that multicollinearity is problematic.
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- Two groups of mice were injected with a measured amount of tumor pulp. The first group of 27 mice was given a high dosage of chemotherapy while the second group of 30 mice was given a low dosage of chemotherapy. After forty days, the first group had an average tumor size of 0.51cc with a variance of 0.10; the second group had an average tumor size of 0.64cc with a variance of 0.045. Were the tumor sizes of group 1 significantly smaller than those of group 2? What is the observed test statistic?Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record their times for 20 commutes. The first worker's times have a variance of 12.2. The second worker's times have a variance of 16.9. The first worker thinks that he is more consistent with his commute times and that his commute time is shorter. Test the claim at the 10% level.What is the F statistic? (Round your answer to two decimal places.)A set of solar batteries is used in a research satellite. The satellite can run on only one battery, but it runs best if more than one battery is used. The variance ?2 of lifetimes of these batteries affects the useful lifetime of the satellite before it goes dead. If the variance is too small, all the batteries will tend to die at once. Why? If the variance is too large, the batteries are simply not dependable. Why? Engineers have determined that a variance of ?2 = 23 months (squared) is most desirable for these batteries. A random sample of 22 batteries gave a sample variance of 15 months (squared). Using a 0.05 level of significance, test the claim that ?2 = 23 against the claim that ?2 is different from 23. (f) Find a 90% confidence interval for the population variance. (Round your answers to two decimal places.) (g) Find a 90% confidence interval for the population standard deviation. (Round your answers to two decimal places.)
- In a research setting, the efficiency of homecare workers (part-time and full-time) were compared. Data is given below. Is there a difference between full-time and part-time homecare workers? (Variances are assumed to be homogenous, α=0.05). Group Efficiency Points Group Efficiency Points Full-time 5 Part-time 1 Full-time 3 Part-time 3 Full-time 4 Part-time 4 Full-time 1 Part-time 4 Full-time 2 Part-time 2 Full-time 3 Part-time 0 Full-time 2A researcher found a significant correlation of .12 between gender (coded as 0 = ‘male’ and 1 = ‘female’) and number of friends at university. If the assigned values of gender were changed to 1 = ‘female’ and 2 = ‘male’, how would this affect the correlation? The strength of the relationship would become weaker The amount of variance explained by the relationship would increase It would become nonsignificantThe sign would change to become negative A researcher is trying to predict anxiety (measured on a 7-point scale) from exposure to stress (operationalised as the number of stressful life events participants can recall in the last week). She has found a correlation coefficient of r = .54 between anxiety and stress, with a standard deviation of 4.45 for anxiety and a variance of 17.21 for stress. What other information is needed to calculate b? The sums of squares of stressThe sums of products of anxiety and stress The covariance of anxiety and stressNo other information is…Explain whether homogeneity of variance is satisfied for this analysis, and be clear on how you decided this.
- Records from previous years for a casualty insurance company show that its clients average a combined total of 1.9 auto accidents per day, with a variance of 0.31. The actuaries of the company claim that the current variance, oʻ, of the number of accidents per day is not equal to 0.31. A random sample of 17 recent days had a mean of 2 accidents per day with a variance of 0.62. If we assume that the number of accidents per day is approximately normally distributed, is there sufficient evidence to conclude, at the 0.05 level of significance, that the actuaries are correct? Perform a two-tailed test. Then complete the parts below. Carry your intermediate computations to three or more decimal places and round your answers as specified below. (If necessary, consult a list of formulas.) (a) State the null hypothesis H, and the alternative hypothesis H,. p H, :0 H, :0 (b) Determine the type of test statistic to use. (Choose one) ▼ D=0 OSO O20 (c) Find the value of the test statistic. (Round…A set of solar batteries is used in a research satellite. The satellite can run on only one battery, but it runs best if more than one battery is used. The variance o of lifetimes of these batteries affects the useful lifetime of the satellite before it goes dead. If the variance is too small, all the batteries will tend to die at once. Why? If the variance is too large, the batteries are simply not dependable. Why? Engineers have determined that a variance of o2 23 months (squared) is most desirable for these batteries. A random sample of 30 batteries gave a sample variance of 15.4 months (squared). Using a 0.05 level of significance, test the claim that o? = 23 against the claim that o is different from 23. (f) Find a 90% confidence interval for the population variance. (Round your answers to two decimal places.) lower limit upper limit (g) Find a 90% confidence interval for the population standard deviation. (Round your answers to two decimal places.) lower limit months upper limit…It is hypothesized that the total sales of a corporation should vary more in an industry with active price competition than in one with duopoly and tacit collusion. In a study of the merchant ship production industry it was found that in 4 years of active price competition, the variance of company A’s total sales was 114.09. In the following 7 years, during which there was duopoly and tacit collusion, this variance was 16.08. Assume that the data can be regarded as an independent random sample from two normal distributions. 1. Test, at the 5% level, the null hypothesis that the two population variances are equal against the alternative that they are not equal.
- QUESTION 4 In general, an experienced quality control inspector of measurement of sheet metal stamping would have a variance of 0.18 (inch)². A new joint inspector measures 101 stampings with variance of 0.165 (inch)². Assume data is normally distributed, by using 95% significance level, test whether the new joint inspector is making satisfactory measurements. QUESTION 5 A marketing study was done on consumer from two age groups for their spending on 20 categories of consumer items. Based on 15 respondents in the 18 – 34 age group, the average spending is RM76.40 with a variance of RM25.30. Meanwhile, based on 18 respondents in the 35+ group, the mean and variance were RM71.20 and RM22.20 respectively. By assuming the population variance are not equal, test if there is any difference in the mean spending between these two populations in 95% significance level.Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record their times for 20 commutes. The first worker's times have a variance of 12.1. The second worker's times have a variance of 16.9. The first worker thinks that he is more consistent with his commute times and that his commute time is shorter. Test the claim at the 10% level. What is s1 in this problem? What is s2 in this problem?A set of solar batteries is used in a research satellite. The satellite can run on only one battery, but it runs best if more than one battery is used. The variance ?2 of lifetimes of these batteries affects the useful lifetime of the satellite before it goes dead. If the variance is too small, all the batteries will tend to die at once. Why? If the variance is too large, the batteries are simply not dependable. Why? Engineers have determined that a variance of = 23 months (squared) is most desirable for these batteries. A random sample of 20 batteries gave a sample variance of 12.8months (squared). Using a 0.05 level of significance, test the claim that ?2 = 23 against the claim that?2 is different from 23.
