5.measurement

Measurement
and
scaling techniques
D.A. Asir John Samuel, MPT (Neuro Paed),
Lecturer, Alva’s college of Physiotherapy,
Moodbidri

Dr.Asir John Samuel (PT), Lecturer, ACP

Data
• Data / variable
Data

Quantitative Qualitative

Discrete Continuous Nominal Ordinal

Quantitative

• Discrete

- Takes only specified no.of values in a given
range

- E.g. No. of birth


Quantitative

• Continuous

- Theoretically can take any value with in given
range

- E.g. BP, Wt, Ht, age,


Qualitative

• Cannot be measured numerically

• Nominal

- No nature order among the categories

- E.g. gender, religion, etc.,


Qualitative

• Ordinal

- Natural ranking of categories

- E.g. severity of diseases, socioeconomic status,


Scales of measurement

Scales

Categorical Numerical

Nominal Ordinal Interval Ratio

Nominal scale
• Lowest level of measurement
• Used for variable that are qualitative
• Variable is divided into several categories
• Frequently allow us to compare no.of items
within each category
• No arithmetic operation are permitted
• E.g. gender, religion, etc.,

Ordinal scale
• Rank order the objects being measured
• Permissible operations are < = >
• No meaning of magnitude of difference
between adjacent units on scale
• Does not have the property of equal intervals
between adjacent units
• No arithmetic equation permitted
• E.g. pain score, disease severity, etc.,

Interval scale
• Have real number system properties of order
and distance but lack origin

• Possess all the properties of the ordinal scale

• Equal intervals b/w adjacent units

• Does not have an absolute zero point

• Permissible arithmetic operation are - & +

• E.g. temp in Celsius, IQ score, etc.,

Ratio scale
• Exhibit all 3 components of real number
system: order, distance and origin

• Highest level of measurement scale

• Possesses all the properties of interval scale

• Has an absolute zero point

• Permissible arithmetic operations are, -, +, x
and /

• E.g. wt, ht, distance, etc.,

Sources of error in measurement

• Respondent

• Situation

• Measurer

• instrument


Respondent

• Reluctant to express strong negative feelings

• May have very little knowledge but may not
admit ignorance

• Result in an interview of guesses

• Limit ability to respond accurately and fully


Situation

• Any condition which places strain on interview

• Affects interviewer-respondent rapport

• Can distort responses by joining in or merely
by being present


Measurer

• Distort responses by rewording or reordering
questions
• Behaviour, style and looks may encourage or
discourage certain replies from respondents
• Incorrect coding
• Data-analysis stage

Instrument

• Defective measuring instrument

• Complex words

• Beyond comprehension

• Poor sampling


Technique of developing measurement
tools
• Four-stage process

- Concept development

- Specification of concept dimensions

- Selection of indicators

- Formation of index


Meaning of Scaling

• A procedure for the assignment of numbers to
a property of objects in order to impart some
of the characteristics of numbers to the
properties in question
• Quantitative measures of subjective abstract
concepts


By 2 ways

• Making judgement

• Constructing questionnaires


Technique of developing
measurement tools

• Concept development

• Specification of concept dimensions

• Selection of indicators

• Formation of index


Concept development

• First and foremost step

• Researcher should arrive at an understanding
of major concepts pertaining to his study

• More apparent in theoretical studies than in
the more pragmatic research


Specification of concept dimensions

• Specify the dimensions of the concepts
developed in first stage

• Accomplished by,

- Deduction

- Correlation of individual dimensions with
concept

Selection of indicators

• Measuring each concept

• Specific questions, scales or devices by which
respondent’s knowledge, opinion, expectation,
etc are measured

• Researcher should consider several alternatives
as there is seldom perfect measure

Formation of index

• Combining several dimensions of concept or
different measurement

• Provide scale values to responses and sum up
the corresponding scores

• Has probability relation to what we really
want to know

Classification of scales
• Subject orientation

• Response form

• Degree of subjectivity

• Scale properties

• Number of dimensions

• Scale construction techniques

Subject orientation

• Measure characteristics of respondent who
completes or to judge stimulus object

• Homogeneous stimuli are presented

• Between stimuli variation is small


Response form

• Classify scales as categorical and comparative

• Categorical scales – rating scales, used when
respondent scores without direct ref. of other

• Comparative scales – ranking scales, used
when comparing b/w two or more objects


Degree of subjectivity

• Subjective personal preferences or simply
make non-preference judgement

• Choosing which person he favours

• Judge which person is more effective


Scale properties

• Classify scales as,

• Nominal

• Ordinal

• Interval

• Ratio scales


Number of dimensions

• Unidimensional or multidimensional scales

• Measure only one attribute of respondent

• Describes concept of attribute space of ‘n’
dimensions


Scale construction techniques

• Arbitrary approach (based on assumption)

• Consensus approach

• Item analysis approach

• Cumulative scales

• Factor scales


Scaling techniques

• Arbitrary scales

• Differential scales/Thurstone-type scales

• Summated scales/Likert-type scales

• Cumulative scales

• Factor scales


Arbitrary scales

• Designed through researcher’s own subjective
selection of items

• Collects few statements or items which he
believes appropriate to a given topic


Arbitrary scales-Merits

• Can be developed very easily and quickly

• Relatively less expensive

• Highly specific and adequate


Arbitrary scales-Demerits

• Do not have objective evidence

• Simply rely on researcher’s insight and
competence


Differential scales/Thurstone-type
scales
• Developed using consensus scale approach

• Selection is made by panel of judges

• Evaluate whether they are relevant to the
topic area


Summated scales/Likert-type scales
• Item analysis approach

• Particular item is evaluated on basis of how it
discriminates b/w those persons whose total
score is high and low

• Items that best meet this sort of
discrimination test are included in final
statement Dr.Asir John Samuel (PT), Lecturer, ACP

Summated scales/Likert-type scales

1. Strongly agree

2. Agree

3. Undecided

4. Disagree

5. Strongly disagree


Advantages

• Easy to construct

• More reliable

• Respondent-centered

• Less time to construct


Disadvantages

• We can simply examine whether respondents
are more or less favorable to a topic
• Interval is not equal
• Total score has little clear meaning
• What they think they should feel rather than
how they do feel

Cumulative scales

• Louis Guttman’s scalogram analysis

• Statement in it form a cumulative series

• Favorable item and unfavorable item

• From total score one can estimate as to how a
respondent has answered individual
statement

Factor scales

• Developed through factor analysis

• Basis of intercorrelations of items


5.measurement

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