Measurement

“If you can’t measure it, you can’t manage it.”

Bob Donath, Consultant

Measurement

Selecting measurable phenomena

Developing a set of mapping rules

Applying the mapping ruleto each phenomenon

Measurement

What is Measured?

Object-things that is experienced and also those that are not very concrete

Properties – Characteristics of the object

Levels of Measurement

OrdinalOrdinal

intervalinterval

RatioRatio

NominalNominal ClassificationClassification

OrderOrderClassificationClassification

OrderOrderClassificationClassification DistanceDistance

Natural OriginNatural Origin

OrderOrderClassificationClassification DistanceDistance

Sources of Error in Measurement

Respondent

InstrumentMeasurer

Situation

Characteristics of a Good Measurement

CriteriaCriteria

Validity

Practicality ReliabilityReliability

ValidityThe ability of a scale to measure what was intended to be measured.

ReliabilityThe degree to which measures are free from random error and therefore yield consistent results.

PracticalityRelates to the economic factors, convenience and interpretability

Characteristics of a Good Measurement

Validity and Reliability

Reliability and Validity on Target

Old Rifle New Rifle New Rifle Sun glare

Low Reliability High Reliability High Reliability Low Validity Validity ? Low Validity(Target A) (Target B) (Target C)

The Goal Of Measurement Validity

Validity

Validity

ContentCriterionRelated

Construct

Concurrent Predictive DiscriminantConvergentFace

Content Validity

Type What is measured? Technique Content Does the measure adequately Judgment measure the concept? Panel Evaluation Content Validity Ratio Face Do experts validate that the Instrument measures what its Name suggests it measures?

Criterion related Validity

Type What is measured? Technique Criterion Does the measure differentiate Correlation based in a manner that helps to predict a criterion variable? Concurrent Does the measure differentiate in a manner that helps to predict a criterion variable currently? Predictive Does the measure differentiate in a manner as to help predict a future criterion?

Quality of Criterion

Relevant (Proper measure) Sales performance measured using the total sales in a

year

Free from bias (Equal opportunity) Must be adjusted according to area, competition and

potential

Reliable (Stable or Reproducible) Monthly sales versus yearly sales

Available (Ease of collection) Cost Difficulty in securing the data

Construct Validity

Type What is measured? Technique Construct Does the instrument tap the Judgment concept as theorized? Correlation of proposed

with established ones Convergent-discriminant

technique Factor Analysis Convergent Do two instruments measuring the same concept correlate highly? Discriminant Does the measure have a low correlation with a variable that is supposed to be unrelated to this variable

Reliability

Reliability

Stability EquivalenceInternal

Consistency

ParallelForm

Inter rater Inter-itemSplitHalf

Test-retest

Reliability (Stability)

Type What is measured? Technique Stability Reliability of a test or instrument Correlation inferred from examinee scores. Same test is administered again after some time to see the stability of the 2 scores Test-retest Same test is administered over a short

interval of less than 6 months

Problems in Test-retest

Time-delays between measurement leads to situational factor changes

Insufficient time between measurements permit the respondents to remember previous answers

Respondent’s discernment of a disguised purpose may introduce bias – opinion related to the purpose but not assessed

Topic sensitivity occurs when the respondent seeks to learn more about the topic before retest

Introduction of other variables – unrelated to the research

Reliability (Equivalence)

Type What is measured? Technique Equivalence Degree to which alternative forms of the Correlation same measure produce same or similar results. Administered simultaneously or with a delay

Parallel forms Same measurement only difference in terms of sequence and wording Inter rater To what extent 2 raters agree on the rating of the same object/characteristics

Reliability (Internal Consistency)

Type What is measured? Technique Internal Degree to which instrument items are Cronbach Alpha Consistency Homogeneous and reflect the same Split half

correlation Underlying constructs. KR20 Inter item Measures the consistency of responses Consistency in a given measurement tool Split- half The measurement tool is split into two halves and the correlation measured

Improving Reliability

Minimize external sources of variation Standardize the condition under which

measurement occurs Use only trained and experienced investigators

and motivated persons Broaden the sample of measurement questions Taken into consideration only extreme

responses then eliminate questions that do not discriminate

Practicality

Economy InterpretabilityConvenience