Deck 13: GlM 2: Comparing Means Adjusted for Other Predictors Analysis of Covariance

Question 1

A music teacher had noticed that some students went to pieces during exams. He wanted to test whether this performance anxiety was different for people playing different instruments. He took groups of guitarists, drummers and pianists (variable = 'Instru') and measured their anxiety (variable = 'Anxiety') during the exam. He also noted the type of exam they were performing (in the UK, musical instrument exams are known as 'grades' and range from 1 to 8). He wanted to see whether the type of instrument played affected performance anxiety when accounting for the grade of the exam.

-Which of the following statements best reflects what the effect of 'Instru' in the output table below tells us?

A)The type of instrument played in the exam had a significant effect on the level of anxiety experienced.
B)The type of instrument played in the exam had a significant effect on the level of anxiety experienced, even after the effect of the grade of the exam had been accounted for.
C)The type of instrument played in the exam did not have a significant effect on the level of anxiety experienced.
D)The type of instrument played in the exam did not have a significant effect on the level of anxiety experienced, even after the effect of the grade of the exam had been accounted for.

Answer 1

The type of instrument played in the exam had a significant effect on the level of anxiety experienced, even after the effect of the grade of the exam had been accounted for.

Question 2

Which of the designs below would be best suited to ANCOVA?

A)Participants were randomly allocated to one of two stress management therapy groups, or a waiting list control group.The researcher was interested in the relationship between the therapist's ratings of improvement and stress levels over a 3-month treatment period.
B)Participants were allocated to one of two stress management therapy groups, or a waiting list control group based on their baseline levels of stress.The researcher was interested in investigating whether stress after the therapy was successful partialling out their baseline anxiety.
C)Participants were randomly allocated to one of two stress management therapy groups, or a waiting list control group.Their baseline levels of stress were measured before treatment, and again after 3 months of weekly therapy sessions.
D)Participants were randomly allocated to one of two stress management therapy groups, or a waiting list control group.Their levels of stress were measured and compared after 3 months of weekly therapy sessions.

Answer 2

C

Question 3

Which of the following best describes how many covariates can be included in an ANCOVA?

A)Only one covariate can be included.
B)You can include as many covariates as you like.
C)It is a good idea to keep the number of covariates to a minimum.
D)A good rule of thumb is to include one covariate fewer than the number of levels of the independent variable, or less.

Answer 3

C

Question 4

Participants were randomly allocated to one of two stress management therapy groups, or a waiting list control group. Their baseline levels of stress were measured before treatment, and again after 3 months of weekly therapy sessions. The researcher decided to run an ANCOVA on her data. What was the covariate?

A)This is not an appropriate design for ANCOVA.
B)Treatment group
C)Baseline stress levels
D)Time

Question 5

A psychologist was interested in the effects of different fear information on children's beliefs about an animal. Three groups of children were shown a picture of an animal that they had never seen before (a quoll). Then one group was told a negative story (in which the quoll is described as a vicious, disease-ridden bundle of nastiness that eats children's brains), one group a positive story (in which the quoll is described as a harmless, docile creature who likes nothing more than to be stroked), and a final group weren't told a story at all. After the story children rated how scared they would be if they met a quoll, on a scale ranging from 1 (not at all scared) to 5 (very scared indeed). To account for the natural anxiousness of each child, a questionnaire measure of trait anxiety was given to the children and used in the analysis.

-Which of the following statements best reflects what the effect of 'Type Of Information' in the table tells us?

A)The type of information given to the children had a significant effect on their fear beliefs.
B)The type of information given to the children did not have a significant effect on their fear beliefs.
C)The type of information given to the children did not have a significant effect on their fear beliefs, even after their natural level of fear had been accounted for.
D)The type of information given to the children had a significant effect on their fear beliefs, even after their natural level of fear had been accounted for.

Question 6

What are the two main reasons for including covariates in ANOVA?

A)1.) To increase within-group error variance and 2.To reduce between-group error variance
B)1.) To reduce within-group error variance and 2.) Elimination of confounds
C)1.) To increase within-group error variance and 2).To correct the means for the covariate
D)1.) 1.To increase between-group variance and 2.) To reduce within-group error variance

Question 7

Imagine we wanted to investigate the effects of three different conflict styles (avoiding, compromising and competing) on relationship satisfaction, but we discover that relationship satisfaction is known to be affected by self-esteem. Which of the following variables would be the covariate in this study?

A)Relationship satisfaction
B)Conflict style
C)Compromising conflict style
D)Self-esteem

Question 8

Which of the following assumptions must be met when conducting an ANCOVA?

A)Homogeneity of regression slopes.
B)The covariate ought to be independent from the experimental effect.
C)All of these
D)The covariate should be linearly related to the dependent variable.

Question 9

A psychologist was interested in the effects of different fear information on children's beliefs about an animal. Three groups of children were shown a picture of an animal that they had never seen before (a quoll). Then one group was told a negative story (in which the quoll is described as a vicious, disease-ridden bundle of nastiness that eats children's brains), one group a positive story (in which the quoll is described as a harmless, docile creature who likes nothing more than to be stroked), and a final group weren't told a story at all. After the story children rated how scared they would be if they met a quoll, on a scale ranging from 1 (not at all scared) to 5 (very scared indeed). To account for the natural anxiousness of each child, a questionnaire measure of trait anxiety was given to the children and used in the analysis.

-The SPSS output is below. What analysis has been used?

A)Independent analysis of variance
B)Repeated-measures analysis of variance
C)Analysis of covariance
D)Mixed analysis of variance

Question 10

A music teacher had noticed that some students went to pieces during exams. He wanted to test whether this performance anxiety was different for people playing different instruments. He took groups of guitarists, drummers and pianists (variable = 'Instru') and measured their anxiety (variable = 'Anxiety') during the exam. He also noted the type of exam they were performing (in the UK, musical instrument exams are known as 'grades' and range from 1 to 8). He wanted to see whether the type of instrument played affected performance anxiety when accounting for the grade of the exam.

- Which of the following statements best reflects what the effect of GRADE in the table tells us?

A)The type of instrument played did not have a significant relationship with the grade of exam that was being taken.
B)The grade of exam had a significant relationship with the level of anxiety experienced.
C)The grade of exam did not have a significant relationship with the level of anxiety experienced.
D)The type of instrument played had a significant relationship with the grade of exam that was being taken.

Question 11

A music teacher had noticed that some students went to pieces during exams. He wanted to test whether this performance anxiety was different for people playing different instruments. He took groups of guitarists, drummers and pianists (variable = 'Instru') and measured their anxiety (variable = 'Anxiety') during the exam. He also noted the type of exam they were performing (in the UK, musical instrument exams are known as 'grades' and range from 1 to 8). He wanted to see whether the type of instrument played affected performance anxiety when accounting for the grade of the exam.

-The first part of the SPSS output is below. What does this part of the output tell us?

A)The grade of exam taken did not have a significant effect on anxiety.
B)The variances of anxiety scores were different in the different groups of musicians.
C)The variances of anxiety scores were roughly the same in the different groups of musicians.
D)The type of instrument played did not have a significant effect on anxiety.

Question 12

Which of the following sentences best describes a covariate?

A)A variable that is not able to be measured directly.
B)A variable that shares some of the variance of another variable in which the researcher is interested.
C)A variable that correlates highly with the dependent variable.
D)A pair of variables that share exactly the same amount of variance of another variable in which the researcher is interested.

Question 13

Imagine we wanted to investigate the effects of three different conflict styles (avoiding, compromising and competing) on relationship satisfaction, but we discover that relationship satisfaction is known to covary with self-esteem.

-Which of the following questions would be appropriate for this analysis?

A)What would the mean relationship satisfaction be for the three conflict style groups, if their levels of self-esteem were held constant?
B)What would the mean relationship satisfaction be if levels of self-esteem were held constant?
C)What would the mean self-esteem score be for the three groups if their levels of relationship satisfaction were held constant?
D)Does relationship satisfaction have a significant effect on the relationship between conflict style and self-esteem?

Question 14

A music teacher had noticed that some students went to pieces during exams. He wanted to test whether this performance anxiety was different for people playing different instruments. He took groups of guitarists, drummers and pianists (variable = 'Instru') and measured their anxiety (variable = 'Anxiety') during the exam. He also noted the type of exam they were performing (in the UK, musical instrument exams are known as 'grades' and range from 1 to 8). He wanted to see whether the type of instrument played affected performance anxiety when accounting for the grade of the exam.

- Which of the following statements best reflects what the tables below tell us?

A)Guitarists were significantly less anxious than pianists and drummers, and drummers were significantly more anxious than pianists.
B)Guitarists were significantly less anxious than drummers, but were about as anxious as pianists, and drummers were about as anxious as pianists.
C)Guitarists were significantly less anxious than pianists and drummers, and drummers were significantly less anxious than pianists.
D)Guitarists, drummers and pianists were all about equally anxious.

Question 15

Imagine we wanted to investigate the effects of three different conflict styles (avoiding, compromising and competing) on relationship satisfaction. We discover that relationship satisfaction is known to covary with self-esteem.

-Conducting an ANCOVA will partial out the variance due to the association between which two variables?

A)Self-esteem and relationship satisfaction
B)Self-esteem and conflict style
C)Conflict style and relationship satisfaction
D)It removes the variance due to the association between all variables.

Question 16

Participants were randomly allocated to one of two stress management therapy groups, or a waiting list control group. Their baseline levels of stress were measured before treatment, and again after 3 months of weekly therapy sessions. Based on the output below, which of the following statements is the most accurate?

A)Levene's test was non-significant, F(2, 12) = .82, p = .47, and so the results must be treated with caution.
B)The type of therapy given did not have a significant effect on stress levels, after baseline stress level had been accounted for, F(2, 11) = 5.98, p = .52.
C)The type of therapy administered had a significant effect on stress levels, even after baseline levels of stress had been accounted for, F(1, 11) = 23.16, p < .001.
D)The type of therapy administered had a significant effect on stress levels, even after baseline levels of stress had been accounted for, F(2, 11) = 5.98, p = .017.

Question 17

Imagine we wanted to compare a group of married couples with a group of non-married couples on levels of relationship satisfaction. After collecting our data, we find that the mean age of our married group (M = 30) was significantly different from the mean age of our non-married group (M = 23). What should we do?

A)Rerun the experiment, making sure to randomize participants to experimental groups.
B)Add 'age' into the analysis as a covariate to obtain a purer effect of marital status.
C)Conclude that the assumption of independence of the covariate and treatment effect has been met.
D)Run a bootstrapped ANCOVA with 'age' as the covariate.

Question 18

Imagine we wanted to investigate the effects of three different conflict styles (avoiding, compromising and competing) on relationship satisfaction. We discover that relationship satisfaction is known to covary with self-esteem, so we conduct an ANCOVA with self-esteem as the covariate. What could be a potential issue with this study?

A)Self-esteem might also be related to relationship satisfaction.
B)Self-esteem might also be related to conflict style.
C)It is possible that there will be a linear relationship between self-esteem and relationship satisfaction.
D)There could be more than three conflict styles.

Question 19

A psychologist was interested in the effects of different fear information on children's beliefs about an animal. Three groups of children were shown a picture of an animal that they had never seen before (a quoll). Then one group was told a negative story (in which the quoll is described as a vicious, disease-ridden bundle of nastiness that eats children's brains), one group a positive story (in which the quoll is described as a harmless, docile creature who likes nothing more than to be stroked), and a final group weren't told a story at all. After the story children rated how scared they would be if they met a quoll, on a scale ranging from 1 (not at all scared) to 5 (very scared indeed). To account for the natural anxiousness of each child, a questionnaire measure of trait anxiety was given to the children and used in the analysis.

-Which of the following statements best reflects what the 'pairwise comparisons' tell us?

A)Fear beliefs were significantly lower after positive information compared to negative information and no information; fear beliefs were not significantly different after negative information compared to no information.
B)Fear beliefs were significantly higher after negative information compared to positive information; fear beliefs were significantly lower after positive information compared to no information.
C)Fear beliefs were all about the same after different types of information.
D)Fear beliefs were significantly higher after negative information compared to positive information and no information, and fear beliefs were not significantly different after positive information compared to no information.

Question 20

A psychologist was interested in the effects of different fear information on children's beliefs about an animal. Three groups of children were shown a picture of an animal that they had never seen before (a quoll). Then one group was told a negative story (in which the quoll is described as a vicious, disease-ridden bundle of nastiness that eats children's brains), one group a positive story (in which the quoll is described as a harmless, docile creature who likes nothing more than to be stroked), and a final group weren't told a story at all. After the story children rated how scared they would be if they met a quoll, on a scale ranging from 1 (not at all scared) to 5 (very scared indeed). To account for the natural anxiousness of each child, a questionnaire measure of trait anxiety was given to the children and used in the analysis.

-Which of the following statements best reflects what the effect of 'Natural Fear Level' in the table tells us?

A)The child's natural level of fear had a significant relationship with their fear beliefs about the animals.
B)The child's natural level of fear did not have a significant relationship with their fear beliefs about the animals.
C)The type of information given to the children had a significant relationship with the child's natural level of fear.
D)The type of information given to the children did not have a significant relationship with the child's natural level of fear.