lecture 5 mcqs

Question 1

1. A study finds a Pearson correlation coefficient (r) of –0.82 between hours of screen time and sleep duration in teenagers. What does this mean?
   A) The relationship is strong and negative
   B) There is no relationship
   C) The variables are positively correlated
   D) The data are curvilinear

Answer 1

A

Question 2

2. Which value of Pearson’s r suggests the weakest linear relationship?
   A) 0.91
   B) –0.73
   C) 0.02
   D) –0.62

Answer 2

C

Question 3

3. A researcher observes a U-shaped relationship between BMI and depression score. What does this suggest?
   A) A strong positive linear correlation
   B) A strong negative linear correlation
   C) A curvilinear relationship
   D) A moderate inverse linear relationship

Answer 3

C

Question 4

4. Which assumption is required for linear regression to be valid?
   A) The predictor variable is normally distributed
   B) Y is normally distributed at each X
   C) X and Y are binary
   D) The correlation must be greater than 0.5

Answer 4

B

Question 5

5. A linear regression model outputs the equation:
   Systolic BP = 100 + 1.5 × (Age in years)
   What does this model predict for someone aged 60?
   A) 190
   B) 130
   C) 160
   D) 100

Answer 5

A

Question 6

6. In multiple linear regression, what does each coefficient (β) represent?
   A) Probability of exposure
   B) Correlation strength
   C) Average change in Y for a unit change in that predictor, holding others constant
   D) Percentage risk difference

Answer 6

C

Question 7

7. Which of the following best defines prevalence?
   A) Number of new cases over time
   B) Proportion of the population with a condition at a point in time
   C) Risk ratio

Answer 7

B

Question 8

8. In a study, 20% of smokers have gum disease vs. 10% of non-smokers. What is the relative risk?
   A) 0.5
   B) 1.0
   C) 2.0
   D) 0.2

Answer 8

C

Question 9

9. What does a relative risk of 1.0 indicate?
   A) Exposure decreases risk
   B) Exposure increases risk
   C) No association between exposure and outcome
   D) The risk is doubled

Answer 9

C

Question 10

10. If the odds of gum disease in smokers is 3:1, and in non-smokers it’s 1:3, what is the odds ratio?
    A) 0.33
    B) 1.0
    C) 3.0
    D) 9.0

Answer 10

D

Question 11

11. What conclusion is appropriate if a 95% confidence interval for an odds ratio is 0.85 to 2.43?
    A) The odds ratio is statistically significant
    B) There is no association between exposure and disease
    C) Cannot rule out chance; the interval includes 1
    D) The odds are 2.43 times higher

Answer 11

C

Question 12

12. Which is true about odds and probabilities?
    A) Odds and probabilities are always equal
    B) Odds are always lower than probability
    C) Odds increase as probability increases, but they are not the same
    D) Probability is odds divided by 2

Answer 12

C

Question 13

13. A randomized trial measures time to recovery after two types of surgery. Which analysis method is most appropriate?
    A) Chi-square test
    B) Logistic regression
    C) Survival analysis
    D) Paired t-test

Answer 13

C

Question 14

14. Why can’t we use a t-test to compare mean time-to-conception between two fertility treatments?
    A) It requires categorical data
    B) It ignores censored data
    C) It assumes no time-varying risk
    D) It overestimates the median

Answer 14

B

Question 15

15. Which scenario is most appropriate for survival analysis?
    A) Measuring average cholesterol levels in smokers vs. non-smokers
    B) Determining the percentage of patients with caries
    C) Comparing time to relapse in two groups of cancer patients
    D) Examining prevalence of gingivitis at baseline

Answer 15

C

Question 16

6. In Kaplan-Meier analysis, what does censoring mean?
   A) The person left the study before the event
   B) The event occurred after the study ended
   C) The participant had the event multiple times
   D) The participant was excluded from the data

Answer 16

A

Question 17

17. In a survival curve, what does a steep drop indicate?
    A) Few participants are left
    B) Many participants experienced the event at that time
    C) There was no event
    D) Everyone was censored

Answer 17

B

Question 18

18. What is a limitation of Kaplan-Meier curves?
    A) They can’t show censoring
    B) They ignore time
    C) They can’t adjust for multiple variables
    D) They cannot be used for survival data

Answer 18

C

Question 19

19. The odds ratio from a case-control study is 2.4 with 95% CI: 1.3–4.1. What can we conclude?
    A) No significant effect
    B) The odds of exposure are higher in cases, statistically significant
    C) Risk is increased by 1.3 times
    D) There is no difference between groups

Answer 19

B

Question 20

20. Which of the following is NOT a reason to use multiple linear regression?
    A) To control for confounding
    B) To test for effect modification
    C) To compare proportions
    D) To improve outcome prediction

Answer 20

c

Question 21

21. A Pearson correlation coefficient of +0.95 between weight and blood pressure suggests:
    A) A weak linear relationship
    B) A strong positive linear relationship
    C) A curvilinear relationship
    D) No relationship

Answer 21

B

Question 22

22. Which of the following would violate the assumptions of linear regression?
    A) Y is normally distributed
    B) Constant variance of residuals
    C) Strong curvilinear relationship
    D) Linearity between X and Y

Answer 22

C

Question 23

23. A regression model estimates:
    Gum bleeding score = 5 + 1.2 × Plaque index
    What happens to bleeding score if plaque index increases by 2 units?
    A) Increases by 2.4
    B) Increases by 1.2
    C) Decreases by 1.2
    D) Increases by 5

Answer 23

A

Question 24

24. What is the difference between correlation and regression?
    A) Correlation only applies to categorical variables
    B) Regression estimates a relationship; correlation quantifies its strength
    C) Correlation is used for predictions
    D) Regression cannot handle continuous variables

Answer 24

B

Question 25

25. In a study, the relative risk of enamel erosion in energy drink consumers vs. non-consumers is 3.2. Which is correct? A) No association is present B) Energy drink consumers are 3.2 times as likely to have erosion C) The study found no statistical difference D) The odds of erosion are 3.2 times higher

Answer 25

B

Question 26

26. A researcher reports the odds of developing fluorosis in one group is 0.4. What does this mean? A) Probability of the event is 60% B) Event is more likely than not C) The odds of occurrence are less than non-occurrence D) There is a 0.4% chance of fluorosis

Answer 26

C

Question 27

27. The odds ratio is best used in which study design? A) Cross-sectional B) Cohort C) Case-control D) Randomized trial

Answer 27

C

Question 28

28. In a survival analysis, censoring occurs when: A) A subject has the event of interest B) A subject drops out or is lost to follow-up C) All subjects are followed to the end D) The study ends before anyone experiences the event

Answer 28

B

Question 29

29. Which is a feature of a Kaplan-Meier survival curve? A) It shows average survival time only B) It displays time-to-event data graphically C) It replaces the need for a hazard ratio D) It applies only to cross-sectional studies

Answer 29

B

Question 30

30. A regression coefficient (β) for sugar intake = 3.4, p = 0.02. Interpretation? A) No significant relationship B) Each gram of sugar intake increases the outcome by 3.4 units, statistically significant C) Sugar intake has no effect D) Each gram of sugar reduces outcome by 3.4 units

Answer 30

B

Question 31

31. A survival study reports median time-to-conception as 5 months. What does this mean? A) Half the women conceived within 5 months B) 5 women conceived C) The first conception occurred at 5 months D) Everyone conceived by 5 months

Answer 31

A

Question 32

32. A confidence interval for a relative risk is 0.8 to 1.2. What can you conclude? A) Strong association present B) Statistically significant at 95% C) Not statistically significant D) Clinically significant

Answer 32

C

Question 33

33. A researcher uses multiple regression to predict gum disease. Which of these is a benefit? A) It eliminates the need for a p-value B) It allows for controlling multiple confounding variables C) It forces all predictors to be binary D) It simplifies interpretation

Answer 33

B

Question 34

34. A correlation of r = 0.00 indicates: A) Strong linear relationship B) No linear relationship C) Perfect curvilinear relationship D) High variability

Answer 34

B

Question 35

35. In which of the following would odds ratio and relative risk be most similar? A) When the event is rare B) When the sample is small C) When risk is 50% or higher D) When the confidence interval is wide

Answer 35

A

Question 36

36. In the Kaplan-Meier curve, a step down indicates: A) An event occurred B) A subject was censored C) A subject dropped out D) Study follow-up ended

Answer 36

A

Question 37

37. Which situation would not be appropriate for survival analysis? A) Time to first cavity B) Time to dropout from a study C) Total number of cavities D) Time to relapse after treatment

Answer 37

C

Question 38

38. Why does the tail of a survival curve flatten out? A) All events occurred early B) It represents patients still at risk but event-free C) No censoring occurred D) Everyone experienced the event

Answer 38

B

Question 39

39. If the hazard is higher in one group, what does this imply on a KM curve? A) Their curve stays higher B) Their curve declines more rapidly C) Their curve is flat D) Their censoring rate is higher

Answer 39

B

Question 40

40. In multiple regression, a non-significant β coefficient means: A) The predictor is not associated with the outcome after adjusting for others B) The correlation is strong C) The sample size is large D) The residuals are unequal

Answer 40

A