# Chapter 8 homework

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Emma Sibley 4,6,10,16,18,22 skip c&d, 24 4. This equation includes the slope (b), which indicates the rate and direction the Y scores change, and the Y intercept (a), which is the value of Y when the line crosses the Y axis and the starting value from the Y scores change. 6. When performing correlation and regression procedures, the X variable is called the predictor and the Y variable is called the criterion. 10. Procedures for describing the relationship when multiple predictor (X variables are simultaneously used to predict scores on one criterion (Y) variable. 16. a. Poindexter finds the correlation between the number of hours studied and the number of errors made on a statistics test as r= 0.80 As the correlation value is close to -1, it depicts a strong negative correlation between them. The correlation between the speed of taking the test and the number of errors made on the test is r= 0.40. The correlation value depicts a moderate negative correlation between them. As 0.40 × 2= 0.80 0.40 × 2= 0.80, it can be said that the correlation value between the number of hours studied and the number of errors made on a statistics test is twice that of the correlation value between the speed of taking the test and the number of errors made on the test. Therefore, statement is correct. b. The correlation between hours studied and the errors made is more (twice) compared to the other correlation, so the number of hours studied is more strongly associated with the errors made, compared to the speed of the test. 18. The correlation coe cient for variables A and B is 0.20 and the correlation coe cient for variables C and B is -0.40. Therefore, a conclusion can be drawn that variables C and B are twice as strongly correlated as variables A and B. Based on the value of r, variables A and B have a relatively weak, positive correlation. The other pair, variables C and B, have a negative correlation, but the correlation is twice as strong. Thus, the relationship between C and B is more useful scientifically. 22. a. b. 24. a. Both study whether and how changes in one variable correlate with changes in another, require careful measurement of at least one uncontrolled variable, should eliminate and/or take account of extraneous variables that might a ff ect those being measured. b manipulation