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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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