Lab Assignment 4 Answers
/28 (1 mark each point unless otherwise specified)
1) Report both the mean and standard deviation of:
a) Neuroticism scores
mean = 2.80 std.dev = 0.50
b) Agreeableness scores
mean = 3.58 std.dev = 0.36
c) Conscientousness scores
mean = 3.46 std.dev = 0.42
2) Create a scatterplot and print output
a)
Perform a bivariate regression analysis predicting Neuroticism from
Agreeableness scores. Report the raw score regression equation.
Y^ = - 0.38x + 4.18
b) Report the standardized regression equation.
Zy^ = - 0.28Zx
c) Report and interpret the coefficient of determination.
- R2 = 0.08
- 8% of the variation in neuroticism is explained by agreeableness
d) Report the value for the multiple correlation (R). 0.28
e) Run a correlation analysis and report the correlation coefficient between
neuroticism and agreeableness. How do these values compare? Explain.
-0.28
- The absolute values are the same because if there is only one predictor, the
multiple correlation coefficient will be the same as the bivariate correlation coefficient
(when there are only 2 variables). The sign is different because R is always positive.
(2 marks)
3a)
Perform a multiple regression analysis predicting Neuroticism scores from both
Agreeableness and Conscientiousness scores.
b) Report the F value. Is the model significant? Report the significance value.
F = 32.13.
The model is significant
p < 0.001 (or p<0.05)
c) Report the multiple correlation (R). By how much has adding conscientiousness as
a predictor changed R?
- R = 0.56 (1 mark)
- 0.564-0.279 = 0.29 increase in R (1 mark)
(0.5 marks if included math and just calculated wrong)
d) Report the standardized beta weights for Agreeableness and Conscientiousness.
Report the significance values for each predictor.
Agree: - 0.18
p = 0.01
Consc: - 0.50
p < 0.001 (or p<0.05)
e) What does the standardized beta weight for agreeableness represent?
For every 1 standard deviation increase in agreeableness, neuroticism
score will change by - 0.18 standard deviations (or will decrease by 0.18
standard deviation units)
f) Which is the better predictor, agreeableness or conscientiousness?
Conscientiousness
g) Amy has an Agreeableness score of 3.63, and a Conscientiousness score of 4.50.
What do you predict her Neuroticism score will be using the unstandardized
regression equation? (Include all work)
y^ = - 0.25 (3.63) - .60(4.5) + 5.769
= - 0.9075 – 2.7 + 5.769
= 2.17
(2 marks: 1 mark if made error in calculation but included work)
Lab 5: Answers:
/46 (one mark each unless otherwise stated)
One Sample
1. A psychologist is testing the hypothesis that completing a data analysis course
may increase your IQ score. We know that the average WAIS IQ score before
taking analysis was 110. After administering the WAIS IQ to all students
successfully completing the data analysis course we obtained 35 scores.
Open the Lab5a.sav file.
H0:(in words) __Population Average Wais IQ score after course is equal to 110_____
H1:_____ Population Average Wais IQ score after course is > 110_ (or not equal to)_
**(want them to say “population” for all the hypotheses)
Mean of WAIS IQ after course: ___118.20_____
std. deviation: ___8.14__________
Create a histogram of the WAIS scores. Print the output. (1 mark)
Mean difference: ____8.20___________
Report the result of the analysis in APA format: __t(34) = 5.96, p <0.001 or p < 0.05
Decision regarding H0: (FAIL TO REJECT or REJECT) ______Reject__________
Independent Samples T-Test
A professor has two introductory psychology classes. In one class he uses the standard
lecture technique and in the other he uses a small-groups discussion technique. He
wonders if it will make a difference on their exam score. He gives the same test to the
two classes and obtains the following data (1=standard lecture, 2=small group discussion)
Open Lab5b.sav.
H0: ___Population average exam score is the same for both standard and small-group discussion
groups_____
H1: ___Population average exam score is different between the standard and small-group
discussion groups______
Standard Lecture exam score: Mean __78.00________
Small Groups exam score: Mean ____64.92_________
std. deviation _14.02___________
std. deviation __15.49___________
Create a bar graph comparing the exam scores of the standard and small group discussion
groups. Print the output. (1 mark for graph)
Conduct an Independent Samples T-Test.
Mean Difference: ____13.08 ____________
Report the result of the analysis in APA format: __t(24)=2.23, p=0.03 or p<0.05_________________
Decision regarding H0: (FAIL TO REJECT or REJECT) _____Reject ____
What is your conclusion (based on what you put for Ho and H1 and the intro):
Using the small-group discussion technique significantly decreases exam scores for an
introductory psychology class compared to standard lecture technique.
What is the range of values that you are 95% confident include the true difference
between the groups?___ (1.12, 25.04)_________________________
Paired Samples
A graduate student at UBC collected some survey data on the perceived competence of
professors before and after lecture training. The graduate student asked ten subjects to
rate the competence of their professors at UBC before and after the training session.
Ratings were collected using the following 7-point Likert rating scale:
Poor
1
2
Average
3
4
5
6
Outstanding
7
Open Lab5c. Generate your null and alternative hypotheses and write them below.
H0:_The population average group ratings for competence of professors before and
after lecture training are equal
H1:_ The population average group ratings for competence of professors before and
after lecture training are not equal
Competence b4 training: Mean __3.80___
std. deviation __2.04__________
Competence after training: Mean ___5.00________ std. deviation __1.70_________
Create a scatterplot using the scores before and after the training session.. Print the
output. (1 mark for graph) – doesn’t matter which variables on which axes
Conduct a Paired Samples T-Test.
Mean Difference: ______- 1.2_______(or 1.2)_____
Report the result of the analysis in APA format: ___t(9)= -1.39, p = 0.20__or p>0.05____________
correlation between before and after training scores: ____r = - 0.06______
Is the correlation significant? _____________yes_______________
Report the significance value: _____0.86___________________
Decision regarding H0: (FAIL TO REJECT or REJECT)_____FAIL TO REJECT___
What is your conclusion (based on what you put for Ho and H1):
Lecture training does not significantly change student ratings of professor competence.
What is the 95% confidence interval of the mean difference___(-3.16, 0.76)__or (-0.76,
3.16)_______?
When do you use an independent vs a paired samples T-Test?
An independent samples t-test is used when you have 2 groups of separate
individuals and you want to compare the group means on some dependent variable.
A paired-samples t-test is used when you have 2 conditions using the same or
matched subjects and you want to compare the mean score between those 2
conditions.
(2 marks – 1 for description of each type of test)
TWO-WAY ANOVA
Using the same data as in the Independent Samples T-Test (5b), pretend that a human
resources person is assessing performance on a psychology 100 exam in classes taught by
four different professors. Each professor teaches two sections of the class, one at 8:30am
and one at 1:00pm. The human resources person wants to know if there is a difference in
class performance between the different professors and between the different class times.
Include a table of means and standard deviations for exam performance for each
professor in each section. (1 mark) – supposed to be from the output (ran estimated
marginal means – but another type of table is fine if they came up with it as long as
the means are the same)
Descriptive Statistics
Dependent Variable:Psychology exam score
classtime
Professor
Mean
8:00am
Dr.Rogers
56.0000
9.89949
2
Dr. Claus
64.0000
15.44345
5
Dr. Clinton
63.6667
12.70171
3
Dr. Hogan
61.0000
12.24745
4
Total
61.9286
12.18110
14
Dr.Rogers
89.0000
8.20569
4
Dr. Claus
78.5000
13.43503
2
Dr. Clinton
83.0000
7.00000
3
Dr. Hogan
76.3333
20.84067
3
1:00 pm
Std. Deviation
N
Total
Total
82.5833
12.30269
12
Dr.Rogers
78.0000
18.71897
6
Dr. Claus
68.1429
15.46424
7
Dr. Clinton
73.3333
14.00952
6
Dr. Hogan
67.5714
16.93967
7
Total
71.4615
15.93796
26
Create a line graph representing exam performance for each professor and each class
time. Different lines should represent different professors and x-axis should be class time.
(1 mark)
Report the following (full statistical details) *its fine if they include confidence
intervals
Main effect of Professor:____F(3,18) = 0.15, p >0.05 (or p = 0.93)__
Main effect of Class Time: __F(1,18) = 14.18, p<0.05____________
Professor X Class Time Interaction:___F(3,18) = 0.58, p >0.05 (or p = 0.64)__ __
Mean Square Error Term: ________176.32__________________
Interpret the results in complete sentences. (2 marks )
There was no significant difference in exam performance between the four different
professors or a significant interaction with class time. All professors had similar
average exam scores. However, the class time affected exam performance, such that
students in sections of the class at 8:30am performed worse than students whose
class time was at 1:00pm, suggesting that regardless of which professor they had,
students performed better on the psychology exam if their class was in the afternoon
than in the early morning.
Collapsing across professors, what was the difference in exam scores between 8:30am
and 1:00pm sections? _________20.54_________