Research Methodology Measurement Scale & Level
Level of measurement
A deadly magnitude 7.3 earthquake had struck Nepal in April 2015. GST is charged and levied on any supply of goods and services made in Malaysia at 6%.
Scales of measurement
- Nominal scale
- Categorical variable
- Represented by number
- E.g., gender, employment status, religion, etc.
- Ordinal scale
- Rank variable (highest to lowest…)
- Distances among scales are different
- Interval scale
- The difference between the two values is meaningful
- Distances among scales are identical
- Ratio scale
- True zero
- Differences between values can be compared meaningfully
Needs to be:
Research Methodology Measurement Scale
Simple Rating Scale
- (1) to rate list of items or (2) to rate how much respondents
- like smtg.
- 1-3? 1-5? 1-7? 1-10? 1-100?
- For greater differentiation
- The higher the number, the more you agree/like
- Psychologist Robert Thurstone
- Equal-appearing intervals
- 11-category scale
- Neutral statement
Likert Scale (summated rating approach)
- Psychologist Rensis Likert
- Strongly agree, agree neutral, disagree and
- strongly disagree
Semantic Differential Scale
How would you rate your mother on these scales?
- “the degree to which a test measures what it is supposed to measure”
- Fundamental consideration
- “the degree to which a test consistently measures whatever it is measuring”
- Fundamental consideration.
Types of validity
- Face validity
- Content validity
- Criterion-related validity (1. concurrent validity & 2. predictive validity)
- Construct validity
- Discriminate validity
- Consequential validity
- Face validity
- Subjective assessment / a subjective judgment
- For instance, you might look at a measure of math ability, read through the questions, and decide that YES, it seems like this is a good measure of math ability (i.e., the label “math ability” seems appropriate for this measure)
- Weak validity BUT IT DOES NOT MEAN IT IS WRONG
2. Content validity
- To which a test measures an intended content.
- TWO types: item validity – whether the test items are relevant to the measurement of the intended content area & sampling validity
- –how well the test samples the total content area being tested.
- E.g., being a good science teacher
- A test score cannot accurately reflect a student’s achievement if it does not measure what the student was taught and is supposed to have learned.
- Determined by expert judgment (content validation)
3. Criterion-related validity
- Concurrent validity
“the degree to which scores on one test are related to scores on a similar, preexisting test administered in the same time frame or to some other valid measure available at the same time.”
- Predictive validity
- “the degree to which a test can predict how well an individual will do in a future situation.”
- For example, the Graduate Record Examination (GRE), International English Language Test System (IELTS), etc.
4. Construct validity
- “What is this test really measuring?”
- Constructs underline the variables that researchers measure. You cannot see a construct; you can only observe its effect.
- convergent validity – Correlation test (Pearson)
- discriminate validity -Factor analysisConvergent Validity
Dependability or trustworthiness
- “the degree to which a test CONSISTENTLY measures whatever it is measuring”
- Is expressed numerically – reliability coefficient (correlation) *1.00
- Internal consistency reliability
- Cronbach’s alpha 70% and above
- Test-retest, Kuder-Richardson 20 (KR 20), split-half reliability