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1. Find the true statement about Research Design:
 a. Research question is the issue that leads to the need for your study;
 b. The hypothesis proposes explanation for an observable phenomenon;
 c. Study sample is usually smaller than the target population;
 d. a and b
 e. a, b, and c
e

2. The statement that “There is no difference of bone loss affected by periodontitis between the control and the experimental groups” fits better for:
 a. Setting of a study
 b. Null hypothesis
 c. Alternative hypothesis
b

3. The key difference between observational study and interventional study is:
 a. Whether the data are collect at one time point only or from multiple time points over time
 b. Whether the study look backward and examine exposures to suspected risk
 c. Whether the researcher intervenes the process
 d. a, b, and c
c

4. A sample of dental students is needed to evaluate National Board examine. You draw at random 1/4 of the students from each of the accredited programs. What is this sample called?
 a. Simple Random Sample
 b. Stratified Sample
 c. Systematic Sample
 d. Convenience Sample
b

5. Sampling frame is a list of all sampling units that cover the whole population and must not overlap.

6. Suppose a researcher conducts an experiment to test a hypothesis. If he doubles his sample size, which of the following will increase?
 I. The power of the test.
 II. The effect size of the test.
 III. The probability of making a type II error.
 a. I only
 b. II only
 c. III only
 d. All of the above
 e. None of above
a

7. Significance level or the type I error is the probability that we reject a null hypothesis when it is false.

8. Find the true statement about data collection:
 a. Data collection is the foundation for all findings, conclusions & inferences
 b. The primary data collection can be done through clinical examination, laboratory
 test, patient survey, and medical record abstraction.
 c. Secondary data collection collects the data that have already been collected by
 someone else and exist somewhere.
 d. a, b
 e. a, b, c
e

9. Logistic regression is used,
 a. To model log odds of a binomial outcome measure as functions of some covariates
 b. To compare means across multiple groups
 c. To model a continuous outcome measure as functions of some covariates
 d. To conduct nonparametric analysis
a

10. A study with low statistical power has a high probability of rejecting the null hypothesis when it is false.

11. Skewness is
 a. A measure that characterizes the relative peakedness or flatness of a distribution
 b. A measure of the asymmetry of the probability distribution of a realvalued random variable
 c. A measure that ranges from 3 to +3
 d. A measure that ranges from 2 to infinity
 e. a and c
 f. a and d
 g. b and c
 h. b and d
g

12. A study was conducted to determine the relationship between flossing and the number of sites that bled on periodontal probing (BOP). Flossing was classified as daily, less than daily, and never. Assuming that number of site of BOP was normally distributed, what statistical method fits the best to formally assess the null hypothesis that daily flosser, less than daily flosser, and never flosser have the same mean number of BOP?
 a. Ttest
 b. Chisquare test
 c. Signtest
 d. ANOVA
d

13. The pulp status (normal, mildly necrotic, moderately necrotic, severely necrotic) is of which following types of measurement?
 a. Nominal
 b. Ordinal
 c. Ratio
 d. Interval
b

14. Which of the following is an estimate of the precision of parameter estimates due to sampling?
 a. Variance
 b. Standard Deviation (SD)
 c. Mode
 d. Standard Error (SE)
d

