Bio 215
Which of the following test/s require/s independence of the data (more than one can be true)?
- *answers * ANOVA and Chi-squared
When should you use the Fisher's exact test instead of the Chi-square test for a 2x3 Contingency
Table (more than one can be true)? - *answers * When the sample size is small (e.g. all of the
cell counts <5)
A dentist is testing if gum disease can be prevented by using mouthwash; he uses a Chisquare
test to identify if there is an association between using mouthwash (categorical variable with
three levels: mouthwash used after all meals, used only after lunch, not used at all) and gum
disease (categorical variable with two levels: gum disease present, not present). What is/are the
null hypothesis/es of this experiment (more than one can be true)? - *answers * Gum disease is
not associated with the use of mouth wash
Gum disease is independent from the use of mouth wash
A and B
If we reject the null hypothesis from Q.3, which is/are true (more than one can be true)? -
*answers * A, B, and C
Given the experiment from Q.3, when are the assumptions of the Chi-square test met (more
than one can be true)? - *answers * When each individual only contributes to one cell of the
contingency table
When each individual is exposed to only one of the mouthwash treatments (either use of
mouth wash after all meals, only after lunch, or not used at all)
A and B
Given the experiment from Q.3, and the Chi-square table of observed values below, what is the
Chi-square (only one can be true)? - *answers * 14.91
, Bio 215
Given the experiment from Q.3, and the Contingency Table from Q.6, what are the degrees of
freedom of this Chi-square test (only one can be true)? - *answers * 2
Given the experiment from Q.3, the Contingency Table from Q.6, the Chi-square you calculated
in Q.6, the degrees of freedom you estimated in Q.7, and the table of the critical values of the
Chi-square distribution on the right which is/are true (more than one can be true)? - *answers
* The critical Chi-square for this test is 5.99 (for a p=0.05) and 9.21 (for a p=0.01)
The calculated Chi-square is > than the critical Chi-square for both significance levels (p=0.01 or
p=0.05)
A and C
Given the results of the Chi-square test in Q.6-8, which is/are true (more than one can be true)?
- *answers * You have enough evidence to reject the null hypothesis
Gum disease is contingent upon the use of mouthwash
A and B
Given the output of the Chi-square on the right, which is testing if the presence of bobcat
(categorical variable with two levels: Absent, Present) is associated with Habitat (categorical
variable with three levels: Rural, Suburban, Urban), which is/are true (more than one can be
true)? - *answers * The habitat type is associated with the presence or absence of bobcats
In urban habitats there are less bobcats present than expected
A and B
Given the experiment and the table from Q. 10, which is/are true, (more than one can be true)?
- *answers * The assumptions of the Chi-square are met (less than 20% of the expected
frequencies are <5)
The degrees for freedom of the Chi-square model are 2
A and C
Which of the following test/s require/s independence of the data (more than one can be true)?
- *answers * ANOVA and Chi-squared
When should you use the Fisher's exact test instead of the Chi-square test for a 2x3 Contingency
Table (more than one can be true)? - *answers * When the sample size is small (e.g. all of the
cell counts <5)
A dentist is testing if gum disease can be prevented by using mouthwash; he uses a Chisquare
test to identify if there is an association between using mouthwash (categorical variable with
three levels: mouthwash used after all meals, used only after lunch, not used at all) and gum
disease (categorical variable with two levels: gum disease present, not present). What is/are the
null hypothesis/es of this experiment (more than one can be true)? - *answers * Gum disease is
not associated with the use of mouth wash
Gum disease is independent from the use of mouth wash
A and B
If we reject the null hypothesis from Q.3, which is/are true (more than one can be true)? -
*answers * A, B, and C
Given the experiment from Q.3, when are the assumptions of the Chi-square test met (more
than one can be true)? - *answers * When each individual only contributes to one cell of the
contingency table
When each individual is exposed to only one of the mouthwash treatments (either use of
mouth wash after all meals, only after lunch, or not used at all)
A and B
Given the experiment from Q.3, and the Chi-square table of observed values below, what is the
Chi-square (only one can be true)? - *answers * 14.91
, Bio 215
Given the experiment from Q.3, and the Contingency Table from Q.6, what are the degrees of
freedom of this Chi-square test (only one can be true)? - *answers * 2
Given the experiment from Q.3, the Contingency Table from Q.6, the Chi-square you calculated
in Q.6, the degrees of freedom you estimated in Q.7, and the table of the critical values of the
Chi-square distribution on the right which is/are true (more than one can be true)? - *answers
* The critical Chi-square for this test is 5.99 (for a p=0.05) and 9.21 (for a p=0.01)
The calculated Chi-square is > than the critical Chi-square for both significance levels (p=0.01 or
p=0.05)
A and C
Given the results of the Chi-square test in Q.6-8, which is/are true (more than one can be true)?
- *answers * You have enough evidence to reject the null hypothesis
Gum disease is contingent upon the use of mouthwash
A and B
Given the output of the Chi-square on the right, which is testing if the presence of bobcat
(categorical variable with two levels: Absent, Present) is associated with Habitat (categorical
variable with three levels: Rural, Suburban, Urban), which is/are true (more than one can be
true)? - *answers * The habitat type is associated with the presence or absence of bobcats
In urban habitats there are less bobcats present than expected
A and B
Given the experiment and the table from Q. 10, which is/are true, (more than one can be true)?
- *answers * The assumptions of the Chi-square are met (less than 20% of the expected
frequencies are <5)
The degrees for freedom of the Chi-square model are 2
A and C
