MEASUREMENT

1
MEASUREMENT

• Level of Measurement
• Nominal measurement
• object is in one and only one
• Ordinal measurement
• ranked data
• Internal measurement
• Ratio measurement
• mean
• standard deviation

2
SCALE TYPES

• Noncomparative scaling
• Line marking/continuous rating scales
• Itemised rating scales
• Number of categories
• Nature and degree of verbal description
• Number of favourable and unfavourable categories
• Specification of neutral position
• Forced or unforced nature of a scale
• Comparative scaling

Likert Scale
3
ValidityAre we measuring what we want to
measure?
ReliabilityreproducibleRandom errorStability
--- Test-retest reliability Internal consistency
4
Validity vs Reliability

• Reliability is a NECESSARY but not SIGNIFICANT
  condition for validity.
• There can be reliability yet not valid.
• A unreliable measurement cannot be valid.

5
Questionnaire Design

• Preliminary Consideration
• what info is required
• exactly who to question
• data collection method
• Asking questions
• write specific questions
• refer to your research question
• how will the info help you answer your question

6
Questionnaire DesignBasic Principles

• Be clear and precise
• Do not overlap response choices and be exhaustive
• Use natural and familiar language
• Do not use words that show bias
• loaded questions
• order bias
• Avoid double-barreled questions
• State explicit alternatives
• Questions should meet criteria of validity and
  reliability
• relevance and memory

7
Constructing the Questionnaire

• Response format
• Open-ended questions
• Itemised (close-ended) questions
• Logical flow
• Introducing the questionnaire
• The first questions
• Demographic questions
• Funnel and inverted-funnel sequences
• Changing topics
• Filter questions

8
Constructing the QuestionnaireLayout
Considerations

• Use of booklets
• Appearance of self-administered questionnaires
• Use of blank space and typeface
• Colour coding
• Question numbering
• Fitting questions on a page
• Interviewer instructions
• Response category format
• Skip instructions