# Doing factorial ANOVA Coursera quiz answers

Qn1. Download the file avatars.csv from the course materials. This file describes a study in which men and women were shown a virtual human avatar that was itself either male of female, and asked to craft a persona and write a day-in-th0life scenario for that avatar. The number of positive sentiments in either description were summed by a blind panel of judges. Examine the data and indicate what kind of experiment design this was.

• A 2 x 2 between-subjects design with factors for sex (M,F) and Avatar (M,F)
• A 2 x2 within-subjects design with factors for ex (M,F) and Avatar (M,F).
• A 2 x 2 mixed factorial design with a between-subjects factor for sex (M,F) and a within-subjects factor for Avatar (M,F).
• None of the above

Qn2. How many subjects took part in this experiment?

Qn3. To the nearest hundredth (two digits), on average how many positive sentiments were expressed for the most positive combination of sex and avatar?
Qn4. Create an interaction plot with Sex on the X-axis and Avatar as the traces. Do the lines cross?

``````Yes
No
``````

Qn5. Create an interaction plot with Avatar on the X-axis and Sex as the traces. Do the line cross?

``````Yes,
No
``````

Qn6. Conduct a factorial ANOVA on positives by sex avatar. To the nearest hundredth (two digits), what is the largest F statistic from such a test? Hint: Use the ez library and its exANOVA function. Pass both Sex and Avatar as the between parameter using a vector created with the “c” function.

Qn7. Which effects are statistically significant in the factorial ANOVA of positives by sex and avatar? (Mark all that apply)

``````Main effect of sex
Main effect of Avatar
Sex * Avatar interaction
None of the above
``````

## Planned Pairwise Comparisons

Qn8. Conduct two planned pairwise comparisons using independent samples t-tests. The first question is whether women produced different numbers of positive sentiments for male avatars versus female avatars. The second question is whether men produced different numbers of positive sentiments for male avatars versus female avatars. Assuming equal variances and using Holm’s sequential Bonferroni procedure to correct for multiple comparisons, what to within a ten-thousandth (four digits) is the lowest corrected p-value from these tests? Hint: You will need conjunctions with ampersands (&) to select the necessary rows for your t.test functions.

Qn9. Which of the following conclusions are supported by the planned pairwise comparisons just conducted? (Mark all that apply.)

``````Women made significantly more positive sentiments about male avatars that they did female avatars
Women made significantly more positive sentiments about female avatars than they did male avatars
Men made significantly more positive sentiments about male avatars than they did female avatars
Men made significantly more positive sentiments about female avatars than they did male avatars
None of the above
``````

Qn10. Download the file notes.csv from the course materials. This file describes a study in which iphone and Android smartphone owners used their phone’s built-in note-taking app and then switched to an add-on third-party app, or vice-versa. The number of words they wrote in their notes apps over the course of the week was recorded. Examine the data and indicate what kind of experiment design this was

``````A 2 x 2 between-subjects design with factors for phone (iPhone, Android) and Notes (Built-in, Add-on).
A 2 x 2 **within-subjects design with factors** for Phone(iPhone, Android) and Notes (Built-in, Add-on)
A 2 x2 mixed factorial design with a between-subjects factor for Phone (iPhone, Andoid) and a within-subjects factor for Notes (Built-in, Add-on).
None of the above``````

Qn11. How many subjects took part in this experiment?

Qn12. To the nearest hundredth (two digits) on average how many words were record with the most heavily used combination of phone and notes?

Qn13. Create an interaction plot with Phone on the X-axis and Notes as the traces, Do the lines cross?

``````Yes
No``````

Qn14. Create an interaction plot with notes on the X-axis and Phones as the traces. Do the lines cross?

``````Yes
No
``````

Qn15. Conduct a factorial ANOVA to test for any order effect that the presentation order of the Notes factor may have had. To the nearest ten-thousandth (four digits), what is the p-value for the order factor from such a test? Hint: use the ez library and its ezANOVA function, passing one between parameter and Order as the withing parameter.

Qn16. In our test of possible order effects, Mauchly’s test of sphericity is irrelevant because our within-subjects factor only has two levels, which cannot present a sphericity violation.

``````True
False
``````

Qn17. Conduct a factorial ANOVA on words by phone and Notes. To the nearest hundredth (two digits), what is the largest F statistic produced by such a test? Hint: use the ez library and its ezANOVA function, passing one between parameter and on within parameter.

Qn18. Conduct two planned pairwise comparisons using paired-samples t-tests. The first question is whether iPhone users entered different numbers of words using built-in notes apps versus the add-on notes app. The second question is whether Android users entered different numbers of words using the built-in notes app versus the add-on notes app. Assuming equal variances and using Holm’s sequential Bonferroni procedure to correct for multiple comparisons, what to within a ten-thousandth (four digits) is the lowest p-value from these tests? Hint: use the reshape2 library and its dcast function to make a wide-format table with columns for subject, phone, Add-on, and Built-in, and then within each phone type, do a paired-samples t-test between the Add-on and built-in columns.

Qn19. Which of the following conclusions are supported by the planned pairwise comparisons just conducted? (Mark all that apply)

``````Android users entered significantly more words using the built-in notes app than theadd-on notes app.
Android users entered significantly more words using the add-on notes app than the built-in notes app.
iPhone users entered significantly more words using the add-on notes app than the built-in notes app.
None of the above

``````