1. Quantitative Research Methodology
Session 2
Variables, Population, and Sampling

2. Variable A characteristic that varies Independent Variable
“the factor that is measured, manipulated, or selected by the experimenter to determine its relationship with an observed phenomenon” (Tuckman, 1999, p.93)

3. Variable (2) 2. Dependent Variable
“a response variable or output” (Tuckman, 1999, p. 93)

4. Variable (3) 3. Moderator Variable
“a special type of independent variable, a secondary independent variable selected to determine if it affects the relationship between the study’s primary independent variable and it dependent variable” (Tuckman, 1999, p. 97).

5. Variable (4) 4. Control Variables
“Factors controlled by the experimenter to cancel out or neutralized any effect they might have on observed phenomena”(Tuckman, 1999, p. 100)

6. Variable (5) 5. Intervening Variable
“a factor that theoretically affects observed phenomena but cannot be seen, measured, or manipulated; its effect must be inferred from the effects of the independent and moderator variable on the observed phenomenon” (Tuckman, 1999, p. 101)

7. Hypotheses
“a prediction of the possible outcomes of a study”(Fraenkel & Wallen, 2007, p. 46).
“a statement about what we expect to happen in a study” (Mackey and Gass, 2005, p. 100).

8. Null and Alternative Hypotheses
Null Hypothesis (H0)
“a neutral statement used as a basis for testing” (Mackey and Gass, 2005, p. 101).
The null hypothesis states that there are no relationships among variables of interests or no differences among groups in a certain outcome. H0

9. Null and Alternative Hypotheses
Alternative Hypothesis (H1 or Ha)
The opposite of what is stated the null hypothesis.
The research hypothesis should be expressed as the alternative hypothesis.

10. Directional and NonDirectional Hypotheses
“A directional hypothesis indicates the specific direction (such as higher, lower, more, or less) that a researcher expect to emerge in a relationship” (Fraenkel and Wallen, 2005, p.48).
“A nondirectional hypothesis does not make a specific prediction about what direction of the outcome of a study will take” (Fraenkel and Wallen, 2005, p.48).

11. Examples
1. Research Question:
Do high-proficiency learners use more language learning strategies than low-proficiency learners?
(Wharton, 2000 in Larson-Hall, 2010, p.39)
Ho: High-proficiency learners do not use more language learning strategies than low-proficiency learners.
Ha: High-proficiency learners use more language learning strategies than low-proficiency learners.
Dependent Variable:
Independent Variable:

12. Examples
2. Hypothesis:
Anxiety affects test performance, but the correlation is markedly lower for students with test-taking experience.
(Fraenkel & Wallen, 2005, p.44)
Dependent variable:
Independent variable:
Moderator variable:

13. Examples
3. Hypothesis:
High school students taught primarily by the inquiry method will perform better on tests of critical thinking than will high school students taught primarily by demonstration method, although the reverse will be true for elementary school students.
(Fraenkel & Wallen, 2005, p.44)

14. Examples
4. Hypothesis:
Among lower class-children, tangible reinforcement conditions will produce significantly more learning than intangible reinforcement conditions

15. Examples
5. Hypothesis:
Teachers given many positive feedback experiences will have more positive attitudes toward children than teachers given fewer positive feedback experiences.

16. Population and Sample
The entire elements of interest in a particular study
Target Population
“The actual population to which a researcher really to generalize…” (Fraenkel & Wallen, 2005, p.93)
Accessible Population
“The population to which a researcher is able to generalize…”
(Fraenkel & Wallen, 2005, p.93)
A subset of the population
Parameter
Numerical measures of a population
Statistic
Numerical measures of a sample

17. Sampling Probability Sampling (Random Sampling)
Nonprobability Sampling (Nonrandom Sampling

18. Random Sampling Methods
Simple Random Sampling
“Every member of the population has an equal and independent chance of being selected”
(Fraenkel & Wallen, 2007, p. 95)
Stratified Random Sampling
“A process in which certain subgroups, or strata, are selected for the sample in the same proportion as they exist in the population “(Fraenkel & Wallen, 2007, p. 96)

19. Random Sampling Cluster Random Sampling
Every groups in the population has the same probability of being selected
Two-Stage Random Sampling
A combination of cluster random sampling and individual random sampling.

20. Nonrandom Sampling Method
Systematic Sampling
“Every nth individual in the population list is selected for inclusion in the sample” (Fraenkel & Wallen, 2007, p. 98)
Convenience Sampling
“A group of individuals who (conveniently) are available for study” (Fraenkel & Wallen, 2007, p. 100)
Purposive Sampling
Selection of sample based on judgment of researchers