CH. 9 MEASUREMENT: SCALING, RELIABILITY, VALIDITY.

CH. 9MEASUREMENT: SCALING,

RELIABILITY, VALIDITY

Scaling

Scaling is a procedure for the assignment of numbers (or other symbols) to a property of objects in order to import some of the characteristics of numbers to properties in question

Methods of Scaling

Rating scales Have several response categories and are

used to elicit responses with regard to the object, event, or person studied.

Ranking scales Make comparisons between or among

objects, events, persons and elicit the preferred choices and ranking among them.

Rating Scales

Dichotomous scale Is used to elicit a Yes or No answer. Nominal scale

Dichotomous Scale

Do you own a car?

YesNo

Rating Scales (Cont’d)

Category scale Uses multiple items to elicit a single

response. Nominal scale

Category Scale

Where in northern California do you reside?

North BaySouth BayEast BayPeninsulaOther (specify:_____________)

Rating Scales (Cont’d)

Likert scale Is designed to examine how strongly

subjects agree or disagree with statements on a 5-point scale.

Interval scale

Likert Scale

My work is very interesting

Strongly disagreeDisagreeNeither agree nor disagreeAgreeStrongly agree

Rating Scales (Cont’d)

Semantic differential scale Several bipolar attributes are identified at

the extremes of the scale, and respondents are asked to indicate their attitudes.

Interval scale

Semantic Differential

Rating Scales (Cont’d)

Numerical scale Similar to the semantic differential scale,

with the difference that numbers on a 5-point or 7-point scale are provided, with bipolar adjectives at both ends.

Interval scale

Numerical Scale

How pleased are you with your new real estate agent?

Extremely 7 6 5 4 3 2 1 ExtremelyPleased Displeased

Rating Scales (Cont’d)

Itemized rating scale A 5-point or 7-point scale with anchors, as

needed, is provided for each item and the respondent states the appropriate number on the side of each item, or circles the relevant number against each item.

Interval scale

Itemized Rating Scale

1 2 3 4 5Very Unlikely Unlikely Neither Unlikely Likely Very Likely Nor Likely

1. I will be changing my job within the next 12 months

Rating Scales (Cont’d)

Fixed or constant sum scale The respondents are here asked to

distribute a given number of points across various items.

Ordinal scale

Fixed or Constant-Sum Scales

Rating Scales (Cont’d)

Stapel scale This scale simultaneously measure both

the direction and intensity of the attitude toward the items under study.

Interval data

Stapel Scales

Rating Scales (Cont’d)

Graphic rating scale A graphical representation helps the

respondents to indicate on this scale their answers to particular question by placing a mark at the appropriate point on the line.

Ordinal scale

Graphic Rating Scales

Ranking Scales Paired Comparison

Used when, among a small number of objects, respondents are asked to choose between two objects at a time.

Paired-Comparison Scale

Ranking Scales (Cont’d) Forced Choice

Enable respondents to rank objects relative to one another, among the alternatives provided.

Forced Choice

Ranking Scales (Cont’d) Comparative Scale

Provides a benchmark or a point of reference to assess attitudes toward the current object, event, or situation under study.

Comparative Scale

Goodness of Measures Reliability

Indicates the extent to which it is without bias (error free) and hence ensures consistent measurement across time and across the various items in the instrument.

Reliability Stability of measures:

Test-retest reliability Parallel-form reliability

Correlation

Internal consistency of measures: Interitem consistency reliability

Cronbach’s alpha Split-half reliability

Correlation

Goodness of Measures (Cont’d)

Validity Ensures the ability of a scale to measure the

intended concept. Content validity Criterion related validity Construct validity

Validity

Content validity Ensures that the measure includes an

adequate and representative set of items that tap the concept. A panel of judges

Validity (Cont’d)

Criterion related validity Is established when the measure

differentiates individuals on a criterion it is expected to predict Concurrent validity: established when the

scale differentiates individuals who are known to be different

Predictive validity: indicates the ability of measuring instrument to differentiate among individuals with reference to future criterion

Correlation

Validity (Cont’d)

Construct validity Testifies to how well the results obtained from the

use of the measure fit the theories around which the test is designed. Convergent validity: established when the scores

obtained with two different instrument measuring the same concept are highly correlated

Discriminant validity: established when, based on theory, two variables are predicted to be uncorrelated, and the scores obtained by measuring them are indeed empirically found to be so

Correlation, factor analysis, convergent-discriminant techniques, multitrait-multimethod analysis

Understanding Validity and Reliability