EBP Week 8

What are variables in research?

Characteristics of individuals, objects, or environmental conditions that can have more than one value

How are variables defined in quantitative studies?

Through operational definitions under controlled conditions

What is an independent variable?

A factor intentionally manipulated by researchers to cause a change in an outcome

In clinical research, what are often independent variables?

Interventions evaluated in experimental and quasi-experimental designs

What are “levels” of an independent variable?

The different forms a variable takes in a study such as high, moderate, and placebo

What are independent variables called in prognostic studies?

Factors or predictors

Are independent variables used in purely descriptive studies?

No, only in studies with a predictive or causal model

What is a dependent variable?

The outcome of interest in a study

What is the goal in intervention studies regarding dependent variables?

To investigate the causal link between an independent variable and a change in the dependent variable

In prognostic studies, how is the dependent variable related to the independent variable?

It is presumed to be predicted by it, not caused by it

What is an extraneous variable?

A factor other than the independent variable that can influence or confound the dependent variable

Give examples of sources of extraneous variables?

Subjects such as fatigue or alertness, investigators such as experience, equipment, and environment such as room temperature

Why must researchers control extraneous variables?

To avoid misleading conclusions about study results

What is measurement in research?

The process of assigning descriptive or numeric values to variables based on defined, consistent rules

What are the four levels of measurement?

Nominal, Ordinal, Interval, Ratio

Describe nominal level of measurement?

Named categories without rank or equal distance such as hair color or sex

What analysis is used for nominal data?

Frequency counts or percentages

Describe ordinal level of measurement?

Ranked order without known equal distance such as satisfaction scale or weight-bearing status

Can mathematical functions be done with ordinal data?

No, because distances between ranks are not known

Describe interval level of measurement?

Numeric values with rank and equal distance but no true zero such as temperature in Celsius or Fahrenheit

What mathematical operations are allowed with interval data?

Addition and subtraction but not multiplication or division

Describe ratio level of measurement?

Has rank, equal distance, and a true zero such as height, weight, or blood pressure

What operations can be done with ratio data?

Addition, subtraction, multiplication, and division

What is a norm-referenced measurement?

Scores compared to a standard from a previously tested group such as growth charts

What is a criterion-referenced measurement?

Scores compared to an absolute standard such as discharge criteria or standardized exams

What is responsiveness?

The ability of a measurement instrument to detect change in a phenomenon

What factors affect responsiveness?

Instrument-to-definition fit, number of values, and standard error of measurement

What is instrument-to-definition fit?

The instrument must match the operational definition of what’s being measured such as a goniometer for joint angles

How does the number of values affect responsiveness?

More scale values increase the chance of detecting change

What is the Standard Error of Measurement (SEM)?

The dispersion of observed scores around a true score where a large SEM means less responsiveness

What is the Minimal Detectable Change (MDC)?

The smallest change that exceeds the SEM of an instrument

What are floor and ceiling effects?

When a scale can’t register lower (floor) or higher (ceiling) scores for individuals

How can floor and ceiling effects be avoided?

By designing instruments with a wide enough scale and clear definitions

What is the Minimal Clinically Important Difference (MCID)?

The smallest change in a treatment effect that is meaningful to the patient and influences management decisions

What is the Guide to PT Practice definition of tests and measures?

The means of gathering information about the patient or client

What do tests and measures help identify and characterize?

• Health condition

• Impairments of body structure and function

• Activity limitations

• Participation

What is an example of a health condition?

Pathology or disease

What is an example of an impairment of body structures and functions?

Aerobic capacity or blood pressure

What is an example of an activity limitation?

Self-care or ADLs

What is an example of participation?

Ability to engage in community, leisure, social, or work roles

What are tests and measures used to establish?

The diagnosis and prognosis

What are tests and measures used to select?

Interventions

What are tests and measures used to document?

Changes in patient or client status

What do tests and measures indicate?

Achievement of outcomes that are the endpoints of care

What is APTA’s Standard for Tests and Measurements definition of measurement?

Numbers assigned to an object, event, or person, or the class to which they are assigned according to rules

What kinds of measurements do PTs obtain?

Many different types, depending on what is being assessed

What are variables?

Characteristics of individuals, objects, or environmental conditions that may have more than one value

What are examples of individual variables?

• Age

• Gender

• Ethnicity

• Pathology type

• Degree of impairment

• Strength

• Flexibility

• Endurance

• Balance

What are examples of object variables?

Nature of diagnostic tests and interventions

What are examples of environmental variables?

Conditions such as temperature or surroundings

In what type of study does the investigator not influence behavior or outcomes?

Non-experimental study

In what type of study does the investigator intentionally manipulate variables?

Experimental or quasi-experimental study

What is an independent variable?

A variable purposefully manipulated by investigators

What happens when there is more than one independent variable?

The study becomes more complex and interactions may occur

What is a factorial design used for?

To account for potential interactions between independent variables

What is a dependent variable?

The outcome of interest that depends on the independent variable

What is an extraneous variable?

A factor other than the independent variable that may influence or confound the dependent variable

What is another name for an extraneous variable?

Confounding variable

Why are controls and statistical adjustments used in research?

To reduce the influence of extraneous variables

What does the levels of measurement continuum range from?

Descriptive to numeric

What is a numeral in measurement?

A symbol or label in the form of a number

What are the four classical levels of measurement?

Nominal, ordinal, interval, and ratio

What three properties define a real number system?

Order, distance, and origin

What does order refer to?

Higher numbers representing greater amounts of what is being measured

What does distance refer to?

Whether the magnitude of differences between adjacent numbers is equal or unequal

What does origin refer to?

Whether zero represents an absence of the quality measured

What is a nominal scale?

Values that are named categories without rank or equal distance

What are characteristics of nominal scale categories?

Mutually exclusive and exhaustive

Are arithmetic operations meaningful with nominal data?

No

What is an example of nominal data?

Yes or no responses, disease present or absent, agree or disagree

What is an ordinal scale?

Categories rank-ordered based on a defined characteristic or property

What do ordinal classifications incorporate?

Greater than and less than relationships

Are intervals consistent or known in ordinal scales?

No

Do ordinal scales have arithmetic properties?

No

What is a clinical concern when summing ordinal data?

Intervals between ranks may not be consistent

What is an interval scale?

A numeric scale with rank and known equal distances but no true zero point

Does zero represent the absence of a characteristic in an interval scale?

No

What is a common example of an interval scale?

Temperature in Celsius or Fahrenheit

Can interval data have positive and negative values?

Yes

What mathematical operations can be performed with interval data?

Addition and subtraction

What is a ratio scale?

A numeric scale with equal distances, rank, and a true zero point

A numeric scale with equal distances, rank, and a true zero point

Addition, subtraction, multiplication, and division

What are examples of ratio data?

Height, weight, force

Is classifying a measurement always straightforward?

No

What is an example of a measurement that may fit more than one level?

Use of an assistive device

What determines the level of measurement?

Qualities of the instrument and the investigator’s intention for its use

What are the two types of reference standards?

Norm-referenced and criterion-referenced

What is a norm-referenced measurement?

Scores compared to scores previously obtained from other individuals

What is a criterion-referenced measurement?

Scores compared to a previously established absolute standard

What is nominal data also called?

Qualitative or categorical data

How is nominal data organized?

Into named categories with no inherent order

What are examples of nominal data?

Colors like red, green, blue;

types of fruit like apple, banana, orange;

gender like male, female

What is ordinal data?

Data where the order matters, but the distance between values is not meaningful or quantifiable

What is an example of ordinal data in race rankings?

1st, 2nd, 3rd place where you know order but not exact time differences

What is an example of ordinal data in survey ratings?

Very dissatisfied, dissatisfied, neutral, satisfied, very satisfied

What is interval data?

Data where the order matters and distances between values are equal and meaningful, but with no natural zero point

What is an example of interval data?

Temperature in Celsius or Fahrenheit where differences are consistent but zero does not mean absence of temperature

What is ratio data?

Data where order matters, distances are equal and meaningful, and there is a natural zero point

What does a zero value represent in ratio data?

The complete absence of the measured attribute

What are examples of ratio data?

Weight, height, age, income