Variables and Hypotheses



Fraenkel J.R. Wallen, N.E

Chapter 3: Variables and Hypotheses


–    Identifying relationships among variables enhances understanding where we may learn what happened, or where or when (and even how) something happened, not only why it happened.

–    Understanding of relationships helps us to explain the nature of the world in which we live and how parts of it are relate by detect connection between them.


What is a Variable?

–    A variable is any characteristic or quality that varies within a class of objects. The individual members in the class of objects must differ or vary to qualify the class as variable.

–    A constant is any characteristic or quality that is identical within a class of objects. Individual members in the class are held constant and not allowed to vary.

Quantitative versus Categorical Variables

–    A quantitative variable is a variable that varies in amount or degree (rather than all or none) along continuum from less to more, but not in kind. Two obvious examples are height and weight. Quantitative variable can often (but not always) be subdivided into smaller unit, for example: length. Besides it, we can assign numbers to different individuals or objects to indicate how much of the variable they posses, for example: variable “interest” of students toward a subject.

–    A categorical variable is a variable that varies only in kind (qualitatively different), not in degree, amount or quantity. Examples: Eye color, gender, religious preference, occupation, position on a baseball team, political party, teaching method, and most kinds of research “treatments” or “methods.”

–    Researchers in education often study the relationship between (or among) either (1) two (or more) qualitative variables; (2) one categorical and one quantitative; or (3) two or more categorical variable.

Independent versus Dependent Variables

–    An independent variable is a variable presumed to affect or influence one or more other variables. Independent variable may be either manipulated or selected. A manipulated variable (experimental or treatment variable) is one that the researcher creates which typically found in experimental studies. In case researchers select an independent variable that already exist, they must locate and select examples of it, rather than creating it.

–    A dependent (or outcome) variable is a variable presumed to be affected by one or more independent variables.

Moderator Variables

A moderator variable is a secondary independent variable that has been selected for study in order to determine if it affects or modifies the basic relationship between the primary independent variable and the dependent variable. The inclusion of this variable in a study (whenever appropriate) can provide considerably more information than just studying a single independent variable.

Extraneous Variables

An extraneous variable is an independent variable that may have unintended effects on a dependent variable in a particular study. There are many possible extraneous variable which their effect need to be controlled or somehow to be eliminated or minimized by holding them constant (doesn’t vary).


What is a Hypothesis?

–    A hypothesis is a prediction of the possible outcomes of study which made before a study commences.

–    Many different hypotheses can come from a single research question.

Advantages of Stating Hypotheses in addition to Research Questions

–    Hypothesis forces us to think more deeply and specifically about the possible outcome of a study. Elaborating on a question by formulating hypothesis can lead to a more sophisticated understanding of what the question implies and exactly what variables are involved.

–    It can involve a philosophy of science. This enables to make specific predictions based on prior evidence or theoretical argument.

–    It helps us see if we are, or are not, investigating a relationship.

Disadvantages of Stating Hypotheses

–    It may lead to a bias, either conscious or unconscious, on the part of the researcher. This is because by stating hypotheses investigators may be tempted to arrange the procedures or manipulate the data in such a way as to bring about a desired outcome.

–    It may sometimes be unnecessary, or even inappropriate, in research project of certain types, such as descriptive surveys and ethnographic studies.

–    It may prevent researchers from noticing other phenomena that might be important to study.

Significant Hypotheses

A significant hypothesis is one that is likely to lead, if it is supported, to a greater amount of important knowledge than a nonsignificant hypothesis. In addition, a significant hypothesis give information thar will be more use for people interested in the research question.

Directional versus Nondirectional Hypotheses

–    A directional hypothesis is a prediction about the specific nature of a relationship (such as higher, lower, more or less), for example: method A is more effective than method B.

–    A nondirectional hypothesis is a prediction that a relationship exists without specifying its exact nature, for example: there will be a difference between method A and method B (without saying which will be more effective). This is usually made when researchers suspect that a relationship exists but has no basic for predicting the direction of the relationship.


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