HOMEWORK
Homework
Lecturer
Homework
3.Whatare the two reasons you can’t conclude you have demonstrated acausal relationship based on correlational research?
Correlationdoes not indicate the causation of the outcome of the variable beingevaluated.
Correlationlacks the ability to explain how the variables under investigationinteract.
18.Aresearcher measures the following scores for a group of people. The Xvariableis the number of errors on a math test, and the Yvariableis the person’s level of satisfaction with his/her performance.
(a)With such ratio scores, what should the researcher conclude aboutthis relationship? (Hint:Computesomething!)
Thereis a relationship between the satisfaction and performance
(b)How well will he be able to predict satisfaction scores using thisrelationship?
89%
Theresults comes from the regression summary
Participant Errors X SatisfactionY
1 9 3
2 8 2
3 4 8
4 6 5
5 7 4
6 10 2
7 5 7
19.Youwant to know if a nurse’s absences from work in one month 1Y2canbe predicted by knowing her score on a test of psychological“burnout” 1X2.
Whatdo you conclude from the following ratio data?
Thereis medium correlation
Absenceis predicted by burnout
Participant Burnout X AbsencesY
1 2 4
2 1 7
3 2 6
4 3 9
5 4 6
6 4 8
7 7 7
8 7 10
9 8 11
21.Aresearcher observes the behavior of a group of monkeys in the zoo. Hedetermines each monkey’s relative position in the dominancehierarchy of the group (1 being most dominant) and also notes eachmonkey’s relative weight (1 being the lightest).
Whatis the relationship between dominance rankings and weight rankings inthese data?
Thereis high correlation
Absenceis WeightbyDominance
Participant Dominance X WeightY
1 110
2 2 8
3 5 6
4 4 7
5 9 5
6 7 3
7 3 9
8 6 4
9 8 1
10102
1.What is the linear regression line?
linearregression is the discovering the bestfitting straight line throughthe focuses. The bestfitting line is known as a regression line
3.Whatis Yrandhow do you obtain it?
Yr isthe data used to obtainthe linearregressionequation
5.
(a)What does the Yinterceptindicate?
Theamount of change according to the change of X and the constant
(b)What does the slope indicate?
Thedirection of the relationship between the Y and the X intercepts
10.Whenare multiple regression procedures used?
Whenthere are there are two or more predictors and the researcher needsto determine the best predictor of the criterion
12.Whatresearch steps must you go through to use the relationship between aperson’s intelligence and grade average in high school so that, ifyou know a person’s IQ, you can more accurately predict theperson’s grade average?
linearregression line
18.Aresearcher finds that the correlation between variable A and variableB is r=+.20.She also finds that the correlation between variable C and variable Bis r=.40.
Whichrelationship is scientifically more useful and by how much?
Correlationbetween b and c
.40
By.60
Therelationship with either a higher positive score or higher negativescore has indicates stronger relationship
19.Youmeasure how much people are initially attracted to a person of theopposite sex and how anxious they become during their first date.
Forthe following ratio data, answer the questions below.
Participant Attraction X AnxietyY
1 2 8
2 6 14
3 1 5
4 3 8
5 6 10
6 9 15
7 6 8
8 6 8
9 4 7

2 6

Compute the statistic that describes the relationship here.
y= 2.035x + 14.67

Compute the linear regression equation.
y= 0.579x + 5.107

What anxiety score do you predict for a person who has an attraction score of 9?
15

When using this relationship, what is the “ average” amount of error you should expect in your predictions?
85%
20.
(a)For the relationship in question 19, what is the proportion ofvariance accounted for?
.89or 89%
Thisis picked from the regression results
(b)What is the proportion of variance not accounted for?
.12%
Thisthe remaining variance subtracted from the 100% of the proportion ofvariance accounted for
(c)Why or why not is this a valuable relationship?
Thereis weak correlation as the scatter plots do not fall too closely onthe path of the linear regression fit.
22.Aresearcher measures how positive a person’s mood is and howcreative he or she is, obtaining the following interval scores:
ParticipantMood X CreativityY
1 10 7
28 6
39 11
46 4
55 5
63 7
77 4
82 5
94 6
10 1 4

Compute the statistic that summarizes this relationship.
y= 1.035x + 11.67

What is the predicted creativity score for anyone scoring 3 on mood?
7
Thisis arrived at after constituting the regression equation

If your prediction is in error, what is the amount of error you expect to have?
64%

How much smaller will your error be if you use the regression equation than if you merely used the overall mean creativity score as the predicted score for all participants?
36%
Reference
Seber,G. A., & Lee, A. J. (2012). Linearregression analysis (Vol.936). John Wiley & Sons.