February 24, 2017

Homework Help: statistics

Posted by Jumbo on Monday, October 14, 2013 at 7:36am.

1. In an ANOVA, one group has a much larger sample mean than the other. The analyst decides to remove this group and to conduct the analysis on the remaining groups only. Which of the following statements is correct?
Select one:
a. This analysis is not correct, as now the estimate of variance will be based on fewer observations and this will not provide the best test.
b. This analysis is doubtful, as the assumptions of ANOVA may now not be satisfied.
c. This analysis is correct but we will no longer be able to compare the largest mean with the other means.
d. This analysis is good, as it allows the analyst now to investigate if there are differences in the means of the remaining groups.

2. An ANOVA for comparing three means is based on equal sample sizes of 10 each. The within sum of squares is 540. Compute the 5% ciritical difference for a Kramer-Tukey procedure. You are given that the corresponding critical vaue from the studentised range distribution is 3.5064. Give your answer to one decimal place.

3. Which one of the following statements is true regarding the equation of regression for the response variable y on the explanatory variable x?
Select one:
a. When x changes by 1 the value of y changes by 1 as well.
b. The equation must be of the form y = ax + b.
c. The equation gives the average value of y for a given value of x.
d. The equation gives the value of y for a given value of x.

4. Which one of the following statements is NOT true regarding the assumptions of regression.
Select one:
a. The error terms are independent.
b. The error terms are normally distributed.
c. The error terms have mean 0.
d. The error terms can have different variances.

5. A simple linear regression analysis is run on 50 observations. What is the degrees
of freedom for residual sum of squares?

6. A linear regression analyis give the regression equation as y = 4.5 x -2. What is the change in y when x decreases by 2? Give your answer to one decimal place.

7. A regression line is fitted to data, where the x variable takes values between 20 and 50. A prediction is to be made for x = 70. Which one of the following is correct?
Select one:
a. The prediction can be made by using the equation of regression.
b. We should not predict outside the the range of x values as the model may not hold outside this range.
c. The prediction will give the value of y as twice the value when x = 35.
d. We will have to use a computer to predict the value of y for the given value of x.

8. Which one of the following is correct.
Select one:
a. Correlation is a measure on linear relationship between variables.
b. A high correlation indicates a good linear relationship between the variables.
c. If the correlation is less than 0.9 then the relationship between the variables in not linear.
d. A correlation of 0 indicates that there is no relationship between the variables.

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