Research

RE SEARCH ME THO DOLOG Y MODULE 3 – PART B MEAS URE MENT

MEASUREMENT  Selecting

observable empirical events

 Using

numbers or symbols to represent aspects of the events

 Applying

a mapping rule to connect the observation to the symbol.

Wh at is M easured? Objects: • Things of ordinary experience • Some things not concrete  Properties: • Characteristics of objects. 

Characteristics of Data  Classification  Order  Distance

(interval between numbers)  Origin of number series.

Data Types Order

Interval

Origin

Nominal none

none

none

Ordinal

yes

unequal

none

Interval

yes

none

Ratio

yes

equal or unequal equal

zero

Nom inal Dat a / S cal e * ** 

Basic Characteristics



Examples



Descriptive





Numbers identify & classify objects



Store types, gender, members in teams



Percentages, Mode



Chi-square, Binomial test

Inferential

Example - Nominal

Runner 7

Runner 11

Runner 3

Ordina l D ata / S ca le * ** 

Basic Characteristics



Examples



Descriptive



Inferential



Numbers indicate relative position of objects but not magnitude of difference



Quality rankings, market position, social class



Percentages, Median



Rank-order Correlation, Friedman ANOVA

Example - Ordinal

Third Place

Second Place

First Place



Basic Characteristics



Differences between objects can be compared; zero point is arbitrary



Examples



Temperature, Attitudes, Opinions, Index numbers



Descriptive



Range, Mean, Standard Deviation



Inferential



Correlation, t-test, ANOVA, Regression, Factor Analysis

In te rva l D ata / Scale ** *

Example - Interval

Rating 8.2

Rating 9.1

Rating 9.6

Ratio D ata / S cale ** * 







Basic Characteristics

Examples



Zero point is fixed; Ratios of scale values can be computed



Length, Weight, Age, Income, Costs, Sales



Geometric & Harmonic Mean



Coefficient of variation

Descriptive Inferential

Example - Ratio

15.2 seconds

14.1 seconds

13.4 seconds

Sources of Meas ur ement Diff erenc es  Respondent  Situational

factors  Measurer or researcher  Data collection instrument.

Characteristics of Sound Measurement  Validity

– Extent to which a test measures what we actually wish to measure  Reliability – Accuracy and Precision of a measurement procedure  Practicality – Wide range of factors of economy, convenience and interpretability.

Validity in Experimentation ***  Internal

Validity:  Measure of accuracy in an experiment  Measures whether the manipulation of the independent variables, or treatments, actually caused the effects on the dependent variable (s).

Validity in Experimentation ***

 External

Validity:  Determination of whether the cause-and-effect relationships found in the experiment can be generalised.

Validity  Content

Validity

 Criterion-Related

•Predictive •Concurrent

 Construct

Validity

Validity.

Conte nt V alid ity  Degree

to which the content of items adequately represent the universe of all relevant items under study  Sometimes called face-validity ***  Methods:

• Judgemental • Panel Evaluation.

Criterio n-R ela te d Va lid ity  Degree

to which predictor is adequate in capturing the relevant aspects of the criterion

 Method:

• Correlation.

Conc urre nt Va lid ity

Description of the present; Criterion data are available at same time as predictor scores.

Pred ic tiv e Va lid ity

Prediction of the future; criterion data are measured after the passage of time.

Cons tru ct Va lid ity  



What accounts for the variance in the measure? Identifies the underlying constructs being measured and how well the test represents it Methods: Judgemental; Correlation; Factor Analysis; Multi-variate Analysis.

Relia bility  Stability

(Test-retest)

 Equivalence  Internal

(Parallel forms)

Consistency (Split-half, KR20,

Cronbach’s alpha).

Tes t-R ete st (Sta bil ity )  Same

test is administered twice to same subjects over an interval of less than six months

 Method:

Correlation.

Stability means one can secure consistent results with repeated measurements with same instrument.

Bias Caused By...   





Time delay between measurements Insufficient time between measurements Respondent thinks there is disguised purpose Respondent forms new opinion before retest (Topic sensitivity) Introduction of moderating variables between measurements.

Parallel Forms (Equivalence) Test

administered simultaneously or with a delay

Method:

Correlation.

Equ iv ale nce 

Concerned with variations at one point in time among observers and samples of items



Interrater Reliability



Delayed equivalent forms (to prevent “order of presentation” effect).

Cr onb ach’s Alph a (Int ernal Con sis ten cy )

 Degree

to which instrument items are homogenous and reflect the same underlying constructs

 Method:

Specialised Correlation formulae.

Improving Reliability Minimise External sources of variation  Standardise conditions under which measurement occurs  Improve investigator consistency  Broaden measurement questions  Add more observers or occasions  Improve internal consistency. 

Practicality 

Economy



Convenience



Interpretability.