Quantitative Quantitative Research Research

MethodologyMethodologySession 2Session 2

Variables, Population, and Variables, Population, and SamplingSampling

VariableVariable

A characteristic that variesA characteristic that varies

1.1. Independent VariableIndependent Variable

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

Variable (2)Variable (2)

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

Variable (3)Variable (3)

3. Moderator Variable3. Moderator Variable

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

Variable (4)Variable (4)

4. Control Variables4. Control Variables

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

Variable (5)Variable (5)

5. Intervening Variable5. Intervening Variable

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

HypothesesHypotheses

““a prediction of the possible outcomes a prediction of the possible outcomes of a study”(Fraenkel & Wallen, 2007, of a study”(Fraenkel & Wallen, 2007, p. 46).p. 46).

“a statement about what we expect to happen in a study” (Mackey and Gass, 2005, p. 100).

Null and Alternative HypothesesNull and Alternative Hypotheses Null Hypothesis (Null Hypothesis (HH00))

“a neutral statement used as a basis for testing” (Mackey and Gass, 2005, p. 101).

The null hypothesis states that there are The null hypothesis states that there are no relationships among variables of no relationships among variables of interests or no differences among groups interests or no differences among groups in a certain outcome. in a certain outcome.

Null and Alternative HypothesesNull and Alternative Hypotheses

Alternative Hypothesis (HAlternative Hypothesis (H1 1 or Hor Haa))

The opposite of what is stated the The opposite of what is stated the null hypothesis. null hypothesis.

The research hypothesis should be The research hypothesis should be expressed as the alternative expressed as the alternative hypothesis.hypothesis.

Directional and NonDirectional Directional and NonDirectional HypothesesHypotheses

““A A directional hypothesis directional hypothesis indicates the indicates the specific direction (such as higher, lower, specific direction (such as higher, lower, more, or less) that a researcher expect to more, or less) that a researcher expect to emerge in a relationship” (Fraenkel and emerge in a relationship” (Fraenkel and Wallen, 2005, p.48).Wallen, 2005, p.48).

““A nondirectional hypothesis does not A nondirectional hypothesis does not make a specific prediction about what make a specific prediction about what direction of the outcome of a study will direction of the outcome of a study will take” (Fraenkel and Wallen, 2005, p.48). take” (Fraenkel and Wallen, 2005, p.48).

ExamplesExamples1. 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:

ExamplesExamples

2. Hypothesis:2. Hypothesis:

Anxiety affects test performance, but the Anxiety affects test performance, but the correlation is markedly lower for students correlation is markedly lower for students with test-taking experience.with test-taking experience.

(Fraenkel & Wallen, 2005, p.44)(Fraenkel & Wallen, 2005, p.44)

Dependent variable:Dependent variable:

Independent variable:Independent variable:

Moderator variable: Moderator variable:

ExamplesExamples

3. Hypothesis:3. Hypothesis:

High school students taught primarily by High school students taught primarily by the inquiry method will perform better on the inquiry method will perform better on tests of critical thinking than will high tests of critical thinking than will high school students taught primarily by school students taught primarily by demonstration method, although the demonstration method, although the reverse will be true for elementary school reverse will be true for elementary school students.students.

(Fraenkel & Wallen, 2005, p.44)(Fraenkel & Wallen, 2005, p.44)

ExamplesExamples

4. Hypothesis: 4. Hypothesis:

Among lower class-children, tangible Among lower class-children, tangible reinforcement conditions will produce reinforcement conditions will produce significantly more learning than significantly more learning than intangible reinforcement conditionsintangible reinforcement conditions

ExamplesExamples

5. Hypothesis:5. Hypothesis:

Teachers given many positive Teachers given many positive feedback experiences will have more feedback experiences will have more positive attitudes toward children positive attitudes toward children than teachers given fewer positive than teachers given fewer positive feedback experiences. feedback experiences.

Population and SamplePopulation and SampleThe entire elements of interest in a particular studyThe entire elements of interest in a particular study

Target PopulationTarget Population““The actual population to which a researcher really to generalize…” (Fraenkel & The actual population to which a researcher really to generalize…” (Fraenkel & Wallen, 2005, p.93)Wallen, 2005, p.93)

Accessible PopulationAccessible Population““The population to which a researcher is The population to which a researcher is ableable to generalize…” to generalize…”

(Fraenkel & Wallen, 2005, p.93)(Fraenkel & Wallen, 2005, p.93)

Target PopulationTarget PopulationA subset of the populationA subset of the population

ParameterParameterNumerical measures of a populationNumerical measures of a population

StatisticStatisticNumerical measures of a sampleNumerical measures of a sample

SamplingSampling

Probability Sampling (Random Probability Sampling (Random Sampling)Sampling)

Nonprobability Sampling (Nonrandom Nonprobability Sampling (Nonrandom SamplingSampling

Random Sampling MethodsRandom Sampling Methods Simple Random SamplingSimple Random Sampling “ “Every member of the population has an equal and Every member of the population has an equal and

independent chance of being selected” independent chance of being selected” (Fraenkel & Wallen, 2007, p. 95)(Fraenkel & Wallen, 2007, p. 95)

Stratified Random SamplingStratified Random Sampling““A process in which certain subgroups, or strata, A process in which certain subgroups, or strata,

are selected for the sample in the same are selected for the sample in the same proportion as they exist in the population proportion as they exist in the population “(Fraenkel & Wallen, 2007, p. 96)“(Fraenkel & Wallen, 2007, p. 96)

Random SamplingRandom Sampling

Cluster Random SamplingCluster Random Sampling

Every groups in the population has Every groups in the population has the same probability of being the same probability of being selectedselected

Two-Stage Random SamplingTwo-Stage Random Sampling

A combination of cluster random A combination of cluster random sampling and individual random sampling and individual random sampling. sampling.

Nonrandom Sampling MethodNonrandom Sampling Method Systematic SamplingSystematic Sampling

““Every nth individual in the population list is selected for Every nth individual in the population list is selected for inclusion in the sample” (Fraenkel & Wallen, 2007, p. 98)inclusion in the sample” (Fraenkel & Wallen, 2007, p. 98)

Convenience SamplingConvenience Sampling

““A group of individuals who (conveniently) are available for A group of individuals who (conveniently) are available for study” (Fraenkel & Wallen, 2007, p. 100study” (Fraenkel & Wallen, 2007, p. 100))

Purposive SamplingPurposive Sampling Selection of sample based on judgment of researchersSelection of sample based on judgment of researchers