Bio 215 EXAM WITH 100% DETAILED
CORRECT ANSWERS 2025/2026 STUDY
SET
Which of the following test/s require/s independence of the data (more than one can be true)? -
CORRECT 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)? - CORRECT 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)? - CORRECT 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)? - CORRECT
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)? - CORRECT 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)? - CORRECT ANSWERS 14.91
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)? - CORRECT 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)? - CORRECT 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)? -
CORRECT 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)? - CORRECT 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)? -
CORRECT 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
CORRECT ANSWERS 2025/2026 STUDY
SET
Which of the following test/s require/s independence of the data (more than one can be true)? -
CORRECT 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)? - CORRECT 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)? - CORRECT 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)? - CORRECT
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)? - CORRECT 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)? - CORRECT ANSWERS 14.91
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)? - CORRECT 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)? - CORRECT 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)? -
CORRECT 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)? - CORRECT 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)? -
CORRECT 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
