Scales and Measurements

Scales and Measurements

1. Qualitative and Quantitative Data

   • Quantitative Data: :Investigation involving the collection of numerical data
     • Need to check data for: Validity, Reliability and Objectivity

2. Collection of Data

   • Need to be able to classify data

3. Levels and Scales of Measurement

   • Ratio: Data measured on a scale with equal intervals and has a true zero that reflects the absence of the measured characteristic
     • Eg. Ruler, Chess stop clock, stadiometer for height
   • Interval: Data measured on a scale with equal intervals and an arbitrary zero (Negative values are possible
     • Eg. Celsius
   • Ordinal: Data are categorized that are able to be ordered into a rank
     • Eg. BORG Scale
   • Nominal: Uses names, labels or numbers to assign data into various categories
     • Eg. The Census

4. Types of Variable

   • Discrete: Limited in its assessment to certain values, usually integers
     • Eg. Heart Beats
   • Continuous: Can assume any level on a continuous scale
     • Eg. Height

5. Descriptive Research

   • Concerned with status and the experimenter doesn't manipulate anything

6. Validity of Measurements; Degrees to which a test or instrument measures what it purports to measure

   • 4 Categories
     • Face/Logical
       • The degree to which a measures obviously involves the performance being measured
       • Test is valid by definition
     • Criterion (Concurrent/Predictive)
       • Degree to which scores on a test are related to some recognised standard or criterion
       • Acceptable agreement between different measurement tools/protocols, one of which 'usually' being a gold standard, the other tool/protocol being easier to administer
       • Eg. Gold Standard Measure of % body fat: DXA
     • Construct
       • Whether the measured variables represent all the indicators of a concept and the variables that are mutually exclusive
         • Eg. Common in questionnaire work (Eg. IQ)
         • Sometimes uses that known difference technique
     • Content
       • The degree to which a test adequately samples what was covered in the course

7. Reliability of Measurement: Acceptable agreement between repeated tests made under similar conditions (Repeatability, Reproductility, Measurement Error and Precision ect.)

8. Objectivity of Measurements

   • The degree to which different testers can obtain the same scores on the same participants
   • Acceptable agreement between different observers
   • Also known as inter-observer reliability or inter-rater reliability