MEASUREMENT SCALES

What are Variables and Measurements

Variables: Characteristics that can take on different values for different members of a group. For example height

Measurements: “Assignment of numbers to Characteristics (variables) of objects, persons or events.”

In statistics and quantitative research

methodology, levels of measurement are

developed by the psychologist Stanley Smith

Stevens.

• Research conclusions are only good when the

measurements are accurate on which they are based.

• The more precise, sensitive the method of measurement,

the better are the results.

IMPORTANCE OF MEASUREMENT

Stevens (1946) classified variables into four levels. These are

referred to as level of measurement, or levels of data.

1. Nominal

2. Ordinal

3. Interval Scale

4. Ratio Scale

Nominal

Interval

Ratio

Attributes are only named; weakest

Attributes can be ordered

Distance is meaningful

Absolute zero

Ordinal

Nominal scale

The nominal type scale, sometimesalso called the qualitative type thatdifferentiates between items orsubjects only on the basis theirnames or categories or qualities.

Examples include gender, nationality, language, style, and biological species.

A nominal scale represents lower

level of measurement.

Such scales classifies persons or objects in to two or more categories.

Nominal scale

• Example: Country of Origin

• 1 = United States 3 = Canada

• 2 = Mexico 4 = Other

Assignment of numbers to the categories has

no mathematical meaning like

However, in this case, it is important to keep in mind that the numbers do not have intrinsic

meaning

Nominal scale

Ordinal scale

An ordinal scale not only classifies subjects but also ranks them in terms of the degree to which they possess a characteristics of interest. An ordinal

scale indicates relative position.

Ordinal scale can determine whether an object has more or less of a characteristic than some other

object. The exact measurement is not available like student A is taller than student B but their actual

heights are not available.

It permits the researcher to rank or order the respondents or their responses

Example of an ordinal scale:

The result of a horse race, which says only which horses arrived first, second, or third

but include no information about race

times.

Common example of

ordinal scale include quality

ranking, socioeconomics

classes, and occupational

status.

Ordinal scale

Interval scales indicate order and also the distance in the order.

Zero point on the interval scale is arbitrary zero, it does not means the complete absence of anything

Examples

Temperature Scale in

Fahrenheit.

The difference in temperature between 20

degrees F and 25 degrees F is the same

as the difference between 76 degrees F

and 81 degrees F

interval scale

Interval scales allow comparisons of the

differences of magnitude (e.g. of

attitudes) but do not allow determinations of the actual strength

of the magnitude.

interval scale

This is the highest level of measurement and has the properties of other three

levels.

This scale has a unique or fixed beginning or true zero point. (complete absence of

the phenomenon being measured)

Ratio scale

For example

heart beats per minute has a very natural zero point.

Zero means no heart beats.

Weight (in grams) is also a ratio variable. Again, the zero value is meaningful, zero grams means the

absence of weight.

Ratio scale

Ratio scale allow comparisons of the differences of magnitude (e.g. of attitudes)

as well as determinations of the actual strength of the magnitude.

Ratio scale

Reliability and Validity

For a research study to be accurate, its findings

must be both reliable and valid.

Criterion for the selection of instruments

Criteria of selecting instruments

include

Is our measure valid?

Is our measure reliable?

Reliability

Research means that the findings would be consistently the same if the study were done over again

Validity

A valid measure is one that provides the information that it was intended to provide. The purpose of a thermometer, for example, is to provide information on the temperature, and

if it works correctly, it is a valid thermometer.

Criterion for the selection of instruments

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