Variables, Hypotheses, Measurement, and Research Purposes
Variables and Hypotheses
An independent variable is thought to influence, affect, or cause variation in another variable. A dependent variable is thought to depend upon or be caused by variation in an independent variable.
Antecedent Variable: An independent variable that precedes other independent variables in time. It could affect the independent variable and alter its relationship to the dependent variable.
Intervening Variable: If the relation between X and Y is not spurious, then the intervening variable helps explain this relation.
A hypothesis is an explicit statement that indicates how a researcher thinks the phenomena of interest are related. Example: More formal education will lead to increased income. Independent Variable (education) → Dependent Variable (income).
Characteristics of a good hypothesis: empirical, general, plausible, specific, consistent with the data, and testable. Otherwise, hypotheses are likely to cause difficulty and make a minimal contribution to scientific knowledge. Hypotheses must specify a unit of analysis, the what or whom is being studied (Individuals, groups, states, organizations, countries).
Measurement
Measurement is the process of observing and recording the observations that are collected as part of a research effort.
- Nominal: Refers to different categories or classifications that are assigned to a particular variable (e.g., religion).
- Ordinal: Assumes that cases vary for a particular indicator according to whether they have more or less of a particular attribute (e.g., education: primary, secondary).
- Interval: Includes all of the information of the preceding levels and adds meaningful intervals between values of the variable.
- Ratio: Involves the full mathematical properties of numbers, where there is an absolute 0 (e.g., age).
Accuracy of Measurements
- Reliability: The extent to which an experiment, test, or measuring procedure yields the same results if repeated.
- Validity: Whether or not it measures what it is supposed to measure.
Relationship: Even if a test is reliable, it may not provide a valid measure.
Purposes of Research
- Exploratory: The initial research into a hypothetical or theoretical idea. Lays the initial groundwork for future research.
- Descriptive: Attempts to explore and explain while providing additional information about a topic. Researchers observe and describe what was observed.
- Explanatory: Attempts to connect ideas to understand cause and effect; it answers questions of why.
Causal Relations
A causal relation (CR) between two events exists if the occurrence of the first causes the other. The first event is called the cause, and the second event is called the effect.
How to Make Valid Causal Inferences
Three main strategies: Covariation, Time order, Elimination of alternative causes.
Spurious Relation
A spurious relation is a relationship in which two events or variables have no direct causal connection, yet it may be wrongly inferred that they do, due to either coincidence or the presence of a certain third, unseen factor.
Necessary and Sufficient Causes
- Necessary cause: Represents a condition that may be present for the effect to follow. Example: Being female is a necessary condition of becoming pregnant (However, it is not a sufficient cause. Otherwise, all women would get pregnant.).
- Sufficient cause: A sufficient cause represents a condition that, if it is present, guarantees the effect in question. Example: Fire is a sufficient condition for smoke. (If there is a fire, there will be smoke. If there is no smoke, there can be no fire. If there is smoke, this may or may not be caused by fire.).
Mill’s Methods
- The method of agreement: If two or more instances of the phenomenon under investigation have only one circumstance in common, the circumstance in which alone all the instances agree is the cause (or effect) of the given phenomenon.
- The method of difference: If an instance in which the phenomenon under investigation occurs and an instance in which it does not occur have each circumstance except one in common, that one occurring only in the former, the circumstance in which the two instances differ is the effect or cause or necessary part of the cause of the phenomenon.