Research Methods in Crime and Justice

Chapter 7Variables and the Structure of

Research

Variables and Hypotheses

• In social science, we use variables to describe the different characteristics of individuals, groups, organizations and social phenomena.

• The manner in which we describe things can sometimes help us understand a problem or phenomenon more precisely.

Variables and Hypotheses

• A variable is any characteristic of an individual, group, organization or social phenomenon that changes.

• A hypothesis is a statement that predicts how a change in one or more variables will cause a change in another variable.

Types of Variables

• Generally, there are three types of variables.– Independent variables– Dependent variables– Intervening variables

• Each type of variable functions differently within a hypothesis.

Independent Variables

• An independent variable is;– the causal variable, or – the variable that a researcher predicts will be the

cause of a change in another variable.

Dependent Variables

• A dependent variable is;– the effect, or – the variable that a researcher predicts will change

as a result of a change in another variable or set of variables.

Independent vs. Dependent

• An easy way to distinguish between the independent and dependent variables is to ask which happens first.

• The independent variable always happens first.

• The first causal rule (temporal order) requires that the cause (independent variable) must happen prior to the effect (dependent variable).

Independent or Dependent?

• Children who experience domestic abuse are more likely as adults to abuse their domestic partners.– Independent variable – Children who experience

domestic abuse.– Dependent variable – domestic abusive behavior

as an adult.

Intervening Variables

• An intervening variable is any variable that – occurs between the independent and dependent

variables, and– may change how, or even if, the independent

variable affects a dependent variable.• In other words, intervening variables intervene

in the causal relationship.

Independent, Dependent or Intervening?

• Children who experience domestic abuse are more likely as adults to abuse their domestic partners, unless they develop strong attachments to non-abusive adults.– Independent variable – Children who experience

domestic abuse.– Dependent variable – domestic abusive behavior as

an adult.– Intervening variable – strong attachments to non-

abusive adults.

Variable Attributes

• Attributes are the different characteristics or values that a variable can take on.

• A variable’s attributes must be both;– Exhaustive– Mutually exclusive

Exhaustiveness

• Exhaustiveness refers to the completeness of the list of attributes.

• All of the possible attributes for each variable must be included.

• In some cases it may be necessary to include an ‘other’ in the list of attributes.

Mutual Exclusivity

• Mutual exclusivity requires that the list of attributes must be we mean that each attribute must be distinctive, such that a respondent can pick one, and only one, option.

Elements of a Good Research Question

• A research question is an interrogative statement. – An actual question– Not a statement

• There are four criteria of a good research question.– Measurable– Unanswered– Feasible– Disinteresting

Elements of a Good Research Question

• Research questions should be measurable. – The concepts in the question should be measurable,

either quantitatively or qualitatively.– Avoid the use of ambiguous terms and superlatives.

• Research questions should be unanswered. – Most questions in the social sciences have been

asked and answered by other researchers. – This does not mean that we cannot ask them again

or in different ways.

Elements of a Good Research Question

• Research questions should be feasible.– Money and time are always finite resources.– Researchers should consider whether a particular

research project is practical or feasible.• Research questions should be disinteresting. – Researchers should be indifferent to the outcome of

their research.– Researchers never should try to prove anything, but

be led by the evidence to the most logical conclusion.

Hypotheses in Social Research

• A hypothesis is a predictive statement that alleges a plausible connection between two or more variables. – ‘Predictive’ means the hypothesis makes a specific

prediction about how two or more variables are connected.

– ‘Plausible connection’ means that the hypothesis must describe the nature of the connection between the variables.

• All hypotheses contain two or more variables.

The Alternative Hypotheses

• An alternative hypothesis (Ha) is a predictive statement alleging a plausible connection between two or more variables.– This is the hypothesis the researcher wants to

confirm as true at the end of the research. – For each alternative hypothesis the researcher

must develop a competing null hypothesis.

The Null Hypothesis

• A null hypothesis (Ho) is a predictive statement that alleges no plausible connection between two or more variables. – The null hypothesis is the exact opposite of the

alternative hypothesis.

Competing Hypotheses

• Alternative hypothesis (Ha): Poor academic performance in the early elementary school years is positively related to juvenile delinquency in the adolescent years.

• Null hypothesis (Ho): Poor academic performance in the early elementary school years is not related to juvenile delinquency in the adolescent years.

The Structure of Research

• In this research project the researcher wants to prove that the alternative hypothesis is a true statement.

• Before doing so, the researcher must first prove that the null hypothesis is a false statement.

The Structure of Research

• If, the data lead the researcher to the conclusion that;– Poor academic performance in the early

elementary school years is not related to juvenile delinquency in the adolescent years (i.e. the null hypothesis).

• Then the researcher will accept the null hypothesis and reject the alternative hypothesis.

The Structure of Research

• If on the other, hand the data lead the researcher to the conclusion that;– Poor academic performance in the early elementary

school years is not related to juvenile delinquency in the adolescent years (i.e. the null hypothesis).

• Is a false statement.• Then, the researcher will reject the null

hypothesis and accept the alternative hypothesis.

Why so Formal?

• Why not just ignore the null hypothesis and try to prove the alternative hypothesis?

• Just as the criminal justice system must presume innocence, so, too, must a researcher presume no relationship between the variables in a research project.

• The formal structure of research is intended to insure the quality of research findings.

Other Types of Hypotheses

• Separate from the distinction between the null and alternative hypotheses, a hypothesis can also be categorized into one of two types. – A hypothesis of association– A hypothesis of difference

• This distinction is important because it determines how the researcher will analyze the data.

The Hypothesis of Association

• A hypothesis of association alleges that a change in the independent variable(s) is associated with a change in the dependent variable. – In most cases the independent variable in a

hypothesis of association will be measured at the ordinal, interval or ratio level of measurement.

– Hence, the data used to test a hypothesis of association can be illustrated in a linear graph.

The Hypothesis of Difference

• A hypotheses of difference alleges that the independent variable(s) makes groups different with respect to the dependent variable. – In most cases the independent variable in a

hypothesis of difference will be measured at the nominal level of measurement.

– Hence, the data used to test a hypothesis of difference can be illustrated in a bar graph.

Getting to the Point

• A variable is any characteristic of an individual, group, organization or social phenomenon that changes.

Getting to the Point

• An independent variable is the causal variable, or the variable that a researcher predicts will be the cause of a change in another variable.

• A dependent variable is the effect, or the variable that a researcher predicts will change as a result of a change in another variable or set of variables.

Getting to the Point

• An intervening variable is any variable that occurs between the independent and dependent variables, changing how, or even if, the independent variable affects a dependent variable.

Getting to the Point

• Attributes are the different characteristics or values that a variable can take on.

• Exhaustiveness refers to the completeness of

the list of a variable’s attributes. • Mutual exclusivity refers to the capacity for a

list of attributes to provide one, and only one, option for each respondent

Getting to the Point

• Good research questions should be;– Measurable, – Unanswered, – Feasible, and – Disinteresting.

Getting to the Point

• A hypothesis is a statement that predicts how a change in one or more variables will cause a change in another variable.

• An alternative hypothesis is a predictive statement that alleges a plausible connection between two or more variables.

• A null hypothesis is a statement that alleges no plausible connection between two or more variables.

Getting to the Point

• A hypothesis of association alleges that a change in the independent variable(s) is associated with a change in the dependent variable. – If the independent variable is ordinal, interval or

ratio, the hypothesis will be one of association. – Hence, the data used to test a hypothesis of

association can be illustrated in a linear graph.

Getting to the Point

• A hypothesis of difference alleges that the independent variable(s) makes groups different with respect to the dependent variable. – If the independent variable is nominal, the

hypothesis will be one of difference. – Hence, the data used to test a hypothesis of

difference can be illustrated in a bar graph.

Research Methods in Crime and Justice

Chapter 7Variables and the Structure of

Research