1. RELIABILITY AND VALIDITY
© LOUIS COHEN, LAWRENCE MANION & KEITH MORRISON

2. STRUCTURE OF THE CHAPTER
Defining validity
Validity in quantitative research
Validity in qualitative research
Types of validity
Triangulation
Validity in mixed methods research
Ensuring validity
Reliability
Reliability in quantitative research
Reliability in qualitative research

3. STRUCTURE OF THE CHAPTER
Validity and reliability in interviews
Validity and reliability in experiments
Validity and reliability in questionnaires
Validity and reliability in observations
Validity and reliability in tests
Validity and reliability in life histories

4. QUANTITATIVE RESEARCH
BASES OF VALIDITY IN
QUANTITATIVE RESEARCH
QUALITATIVE RESEARCH
Controllability
Natural
Isolation, control, manipulation of
Variables
Thick description
Replicability
Uniqueness
Predictability
Emergence, unpredictability
Generalizability
Context-freedom
Context-boundedness
Fragmentation and atomization
Holism
Randomization of samples
Purposive sample/no sampling
Neutrality
Value-ladenness of observations
Objectivity
Confirmability
Observability
Observable and non-observable
meanings/ intentions
Inference
Description, inference, explanation
‘Etic’ research
‘Emic’ research
Observations
Meanings

5. BASES OF RELIABILITY IN QUANTITATIVE RESEARCH
QUALITATIVE RESEARCH
Reliability
Dependability
Demonstrability
Trustworthiness
Stability and replicability
Parallel forms
Context-freedom
Context-specificity
Objectivity
Authenticity and confirmability
Coverage of domain
Comprehensiveness of situation
Verification of data and analysis
Honesty and candour
Answering research questions
Depth of response
Meaningfulness to the research
Meaningfulness to respondents
Parsimony
Richness
Internal consistency
Credibility
Generalizability
Transferability
Inter-rater reliability & triangulation
Inter-rater reliability and triangulation
Accuracy and precision
Accuracy and comprehensiveness
Neutrality
Multiple interests represented
Consistency
Alternative forms (equivalence)
Split-half and inter-item correlation

6. VALIDITY IN QUANTITATIVE AND QUALITATIVE RESEARCH
Validity in quantitative research often concerns: objectivity, generalizability, replicability, predictability, controllability, nomothetic statements.
Validity in qualitative research often concerns: honesty, richness, authenticity, depth, scope, subjectivity, strength of feeling, catching uniqueness, idiographic statements.

7. TYPES OF VALIDITY Catalytic Concurrent Consequential Construct Content
Criterion-related
Convergent & discriminant
Cross-cultural
Cultural validity
Descriptive
Ecological
Evaluative
External
Face
Internal
Interpretive
Jury
Predictive
Systemic
Theoretical

8. VALIDITY IN QUANTITATIVE RESEARCH
Concurrent
Construct
Content
Criterion-related
Convergent & discriminant
Cross-cultural
Evaluative
External
Face
Internal
Jury
Predictive
Theoretical

9. VALIDITY IN MIXED METHODS RESEARCH
Representation
Legitimation
Sample integration
Inside-outside
Weakness minimization
Sequential
Conversion
Paradigmatic mixing
Commensurability
Multiple validities
Political
Integration (of methods)

10. TESTING THREATS TO VALIDITY AND RELIABILITY MATURATION HISTORY
DIRECTION
OF CAUSALITY
INSTRUMENT-
ATION
THREATS TO
VALIDITY AND
RELIABILITY
TYPE 1 AND
TYPE 2
ERRORS
EXPERIMENTAL
MORTALITY
OPERATIONAL-
IZATION
CONTAMIN-
ATION
REACTIVITY

11. ESTABLISHING VALIDITY IN QUALITATIVE RESEARCH
Prolonged engagement in the field
Persistent observation
Triangulation
Leaving an audit trail
Respondent validation
Weighting the evidence (giving priority)
Checking for representativeness
Checking for researcher effects
Making contrast/comparisons
Theoretical sampling
Checking the meaning of outliers
Using extreme cases

12. ESTABLISHING VALIDITY IN QUALITATIVE RESEARCH
Ruling out spurious relations
Replicating a finding
Referential adequacy
Following up surprises
Structural relationships
Peer debriefing
Rich and thick description
Looking for possible sources of invalidity
Assessing rival explanations
Negative case analysis
Confirmatory data analysis
Effect sizes

13. THREATS TO VALIDITY IN QUANTITATIVE RESEARCH
History
Maturation
Statistical regression
Testing
Instrumentation
Selection Bias
Experimental mortality
Instrument reactivity
Selection-maturation interaction
Type I and Type II errors

14. VALIDITY PROBLEMS IN CROSS-CULTURAL RESEARCH
Failure to operationalize elements of cultures
Whose construction of ‘culture’ to adopt: ‘emic’/‘etic’
False attribution of causality to cultural factors rather than non-cultural factors
Directions of causality
Ecological fallacy
Sampling and instrumentation
Convergent and discriminant validity
Response bias and preparation of participants
Language problems
Problems of equivalence (conceptual, psychological, meaning, instrument, understanding, significance, relevance, measurement, linguistic)

15. THREATS TO EXTERNAL VALIDITY IN QUANTITATIVE RESEARCH
Failure to describe independent variables explicitly
Lack of representativeness of available and target populations
Hawthorne effect
Inadequate operationalizing of dependent variables
Sensitization/reactivity to experimental/research conditions
Interaction effects of extraneous factors and experimental/ research treatments
Invalidity or unreliability of instruments
Ecological validity
Multiple treatment validity  

16. THE HAWTHORNE EFFECT
Between 1927 and 1932 researchers carried out experiments at the Western Electric Company’s Hawthorne plant.
Purposes: To examine the effects of changes of working conditions on output of workers
Sample: Six women, chosen as average workers
Method: Women worked in a test room. Output measured under different conditions (e.g. no change → change to method of payment → introduce two rest periods → introduce six rest periods → changes in lighting conditions, early clocking-off, five-day working week → return to initial conditions
Duration: 15 weeks

17. THE HAWTHORNE EFFECT
Results: Output rose steadily during test period and after the test period.
Conclusion: Output did not seem to depend on test conditions. Increased output seemed to be due to the fact that the people had been involved in the experiment itself, i.e. the act of research had affected the results. The results were a research of the research itself.
Implications: The act of being involved in research itself affects the results.

18. THREATS TO EXTERNAL VALIDITY IN QUALITATIVE RESEARCH
Selection effects
Setting effects
History effects
Construct effects

19. ENSURING VALIDITY AT THE DESIGN STAGE
Choose an appropriate time scale;
Ensure adequate resources for the research
Select appropriate methodology
Select appropriate instruments
Use an appropriate sample
Ensure reliability
Select appropriate foci
Avoid having biased researcher(s)

20. ENSURING VALIDITY AT THE DATA COLLECTION STAGE
Reduce the Hawthorne effect
Minimize reactivity
Avoid drop-out rates amongst respondents
Take steps to avoid non-return of questionnaires
Avoid too long or too short an interval between pre-tests and post-tests
Ensure inter-rater reliability
Match control and experimental groups
Ensure standardized procedures for gathering data
Build on the motivations of respondents
Tailor instruments to situational factors
Address researcher characteristics

21. ENSURING VALIDITY AT THE DATA ANALYSIS STAGE
Use respondent validation;
Avoid subjective interpretation of data
Reduce the halo effect
Use appropriate statistical treatments
Recognize extraneous factors which may affect data
Avoid poor coding of qualitative data
Avoid making inferences/generalizations beyond the data
Avoid equating correlations and causes
Avoid selective use of data
Avoid unfair aggregation of data
Avoid degrading the data;
Avoid Type I and/or Type II errors

22. ENSURING VALIDITY AT THE DATA REPORTING STAGE
Avoid using data selectively and unrepresentatively
Indicate the context and parameters of the research
Present the data without misrepresenting the message
Make claims which are sustainable by the data
Avoid inaccurate or wrong reporting of data
Ensure that the research questions are answered
Release research results neither too soon nor too late

23. RELIABILITY IN QUANTITATIVE AND QUALITATIVE RESEARCH
Reliability in quantitative research:
consistency (stability), accuracy, predictability, equivalence, replicability, concurrence, descriptive and causal potential.
Reliability in qualitative research:
accuracy, fairness, dependability, comprehensiveness, respondent validation, ‘checkability’, empathy, uniqueness, explanatory and descriptive potential, confirmability.

24. TYPES OF RELIABILITY IN QUANTITATIVE RESEARCH
Reliability as stability:
Consistency over time and samples;
Reliability as equivalence:
Equivalent forms of same instrument;
Inter-rater reliability;
Reliability as internal consistency:
Split half reliability (e.g. for test items)

25. TRIANGULATION Methodologies Instruments Researchers Time Location
Theories
Samples
Participants
Data

26. SPLIT-HALF RELIABILITY (Spearman-Brown)
r = the actual correlation between the two halves of the instrument (e.g. 0.85);
Reliability = = = 0.919

27. RELIABILITY IN QUALITATIVE RESEARCH
Credibility
Neutrality
Confirmability
Dependability
Consistency
Applicability
Trustworthiness
Transferability

28. RELIABILITY AND REPLICATION IN QUALITATIVE RESEARCH
Repeat:
The status position of the researcher
The choice of informants/respondents
The social situations and conditions
The analytic constructs used
The methods of data collection and analysis
Address:
Stability of observations
Parallel forms
Inter-rater reliability
Respondent validation

29. IMPROVING RELIABILITY
Minimise external sources of variation;
Standardise conditions under which measurement occurs;
Improve researcher consistency;
Broaden the sample of measurement questions by:
adding similar questions to the instrument;
increasing the number of researchers (triangulation);
increasing the number of occasions in an observational study.
Exclude extreme responses (outliers).

30. RELIABILITY AND VALIDITY AT ALL STAGES
Design and methodology
Sampling
Instrumentation
Timing
Data collection
Data analysis
Data reporting