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Nursing Research (FBNG) Spring 2012 Dr. Susan Norwood
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Page 1: Variables in Research

Nursing Research (FBNG)

Spring 2012

Dr. Susan Norwood

Page 2: Variables in Research

Overview of content What variables are

Why this information is important

Types of variables

Defining variables

Research purposes and variables

Theoretical frameworks and variables

Variables and doing a literature review

Practice!

Page 3: Variables in Research

What are we talking about? A “variable” is something that can be different among a

study’s participants or that can change as a part of a study.

All studies have variables.

There are different types of variables –

each is managed differently or has different

roles in the research process.

Page 4: Variables in Research

Why this is important – Different types of variables are managed in different

ways -- you need to know what to do with the different variables in your study.

Implications for research design (study organization)

Implications for data collection (what you will measure)

Implications for enhancing study credibility (research control strategies)

Implications for needed data analysis procedures

Page 5: Variables in Research

Types of variables • Independent variables

• Dependent variables

• Extraneous variables

• Demographic variables

Page 6: Variables in Research

Independent variables The cause in a presumed cause and effect

relationship.

• The study intervention or treatment

• The situation that is expected to result in a certain outcome.

• May be introduced and manipulated by the researcher (experimental variable)

• May be naturally occurring.

• May be under the control of the study’s participants.

Page 7: Variables in Research

Dependent variables The effect in a cause and effect relationship.

• The results or outcome of a treatment or intervention.

• Differences in amounts or qualities of the dependent variable depend on differences in the independent variable.

X Y

Page 8: Variables in Research

Extraneous variables Variables in a research situation that exert an

unintended effect on the dependent variable.

Extraneous variables are not a part of a planned intervention or experiment

Function as rival explanations for a study outcome.

Can be considered nuisance or “noise” factors.

z z z z z

X Y

Page 9: Variables in Research

Extraneous variables, con’t

A confounding variable (or confounder) is a special type of extraneous variable.

Confounding occurs when the association between an independent and dependent variable (cause and effect relationship) is either partly or completely due to a third factor that is not a part of the experiment.

Confounders are related to the independent variable and have a known independent causal effect on the dependent variable.

Page 10: Variables in Research

Extraneous variables, con’t

An example of confounding –

Caffeine consumption during pregnancy

Cigarette smoking

Low birthweight infant

Page 11: Variables in Research

Extraneous variables, con’t

The Independent variable is the real cause –

Confounder present

Confounder absent

Independent variable present

++++++ ++++++

Independent variable absent

++

Page 12: Variables in Research

Extraneous variables, con’t

The confounder is the real cause –

Confounder present

Confounder absent

Independent variable present

++++++ ++

Independent variable absent

++++++

Page 13: Variables in Research

Demographic variables Characteristics of a study’s participants.

• Often function as extraneous variables.

• Sometimes seem to function as an “independent” variable.

Important demographic variables – age, sex, education, socioeconomic status, race/ethnicity, health status

Page 14: Variables in Research

Researcher roles with different variables -- Independent variables – must be consistently applied

Dependent variables – must be carefully measured

Extraneous variables – must be recognized and controlled, if possible

Demographic variables – must be documented; sometimes are controlled.

Page 15: Variables in Research

Defining variables All variables need to have both a conceptual definition

and an operational definition –

Conceptual definition – the “thinking” definition of a variable. A description of the concept that is the foundation of the variable; involves using other concepts. The “mental picture” of the variable that the researcher is using.

Example – “Pain is conceptualized as a

subjective feeling of discomfort.”

Page 16: Variables in Research

Defining variables, con’t

Operational definition – the “measurement definition” of a variable. A description of how the quality or amount of a variable will be determined for the purposes of the study.

Example – “Pain will be operationalized as the participant’s self-report of amount of pain, as reported on a 0 to 10 point scale, where 0 indicates no pain at all and 10 indicates the worst pain imaginable.”

Page 17: Variables in Research

Defining variables, con’t

Discrete versus continuous variables –

Discrete variables – variables that differ in terms of quality or characteristics.

• When “measured,” these variables are placed into categories.

• Categories represent differences in quality (nominal-level data) or in relative amount (ordinal-level data).

Examples – sex, mild/moderate/severe pain

Page 18: Variables in Research

Defining variables, con’t

Continuous variables – variables that differ in amount.

• Measurement of these variables reflects how much of the variable is present, in absolute terms.

• The measurement values fall along a continuum.

• These variables constitute interval or ratio-level data.

Examples – pulse rate, temperature, length of hospitalization, number of falls.

Page 19: Variables in Research

Research purposes and variables -- • All research has extraneous variables!

• Cause and effectiveness research has independent and dependent variables.

• Descriptive research focuses on single “research variables.”

• Correlational research focuses on linkages between pairs (or sets) of variables.

• Predictive research has “predictor” and “outcome” variables.

Page 20: Variables in Research

Research purposes and variables, con’t

Three conditions for detecting a cause and effect relationship –

Temporality – the independent variable (or how it changes) must take place before the dependent variable (and its changes).

Influence – the effect of the independent variable on the dependent variable can be detected with statistics, and the probability that the relationship was caused by chance is small.

Specificity – rival explanations for the observed relationship between the independent and dependent variable can be ruled out.

Page 21: Variables in Research

Theoretical frameworks and variables -- A theoretical framework is an explanation of how

different concepts are related to one another.

• The ideas to be tested in a study

• The hunches and assumptions that guide a study

• A “map” of how the different concepts in the research problem are linked to each other

Concepts are too abstract to be measured directly – so they are translated into variables.

Page 22: Variables in Research

Variables and doing a literature review -- Variables can be useful as search terms for doing a

literature review !

• Intervention of interest (independent variable)

• Outcome of interest (dependent variable)

• Population of interest (demographic variables)

Page 23: Variables in Research

Let’s practice --

Page 24: Variables in Research

Question #1 -- Identify the independent variable in the following

research question: “How does effectiveness of smoking cessation education for teenage boys differ when it is provided by nurses compared to physicians?”

a. Smoking cessation education

b. Teenage boys

c. Type of provider (nurse or physician)

Page 25: Variables in Research

Question #2 -- Identify the dependent variable in the following research

question: “How does gender of health care provider affect compliance with iron supplementation among pregnant women?”

a. Compliance

b. Gender of provider

c. Pregnant women

Page 26: Variables in Research

Question #3 -- Identify the independent variable in the following

research question: “Does average hours of sleep per night differ for second term MSN students who are married versus not married?”

a. Hours of sleep

b. Marital status

c. Term in MSN program

Page 27: Variables in Research

Question #4 -- “The purpose of this study is to explore the relationship

between teen age girls’ participation in sports and self esteem.” What is the independent variable in this study?

a. Participant gender

b. Participation in sports

c. Self esteem

Page 28: Variables in Research

Question #5 -- Which of the following would be operational definition

for obesity?

a. A body mass Index (BMI) of > 30

b. A condition characterized by excess body fat.

c. A risk factor for a variety of health conditions.

Page 29: Variables in Research

Question #6 -- Which of the following statements is an example of a

conceptual definition?

a. Depression is defined as a subjective sensation of pervasive sadness.

b. Depression is differentiated as situational or nonspecific.

c. Depression is determined by score on

the Beck Depression Inventory.

Page 30: Variables in Research

Question Question #7 -- A research report states, “Heart rate was recorded as

beats per minute counted by palpating the radial pulse for 15 seconds and multiplying by 4.” This statement is an example of a(an)

a. conceptual definition

b. intervention or research protocol

c. operational definition.