- Education and Science
Scales for measurement of variables
Continued from: Operational Definition
To measure is to assess, quantify, analyze or appraise. It is to discover the extent, dimensions, capacity and quantity of any physical object.
Business research deals with physical objects as well as ideas. “How sound is an idea” is parallel to assessing “how well you like a song, a painting or personality of your boss”. While physical objects are measured directly, ideas or concepts are measured with the help of an operational definition. Obviously, salesmanship cannot be measured directly but it is easy to set a benchmark for a good salesman as one having sold 200 cars per year without any complaint.
Four scales are used to measure any object or to quantify any concept or idea or properties. These are discussed as follows:
It is just a label having no intrinsic value or quality. It cannot be used in grading or ranking, There are no overlaps and nominal scale are mutually exclusive. One can be either Muslim or non-Muslim, not both at the same time as it requires an item to be placed in one and only one class. It is used for counting or cross-tabulation.
Hair could be black or grey, blood can be A,B,O or AB. In cricket, there is left arm or right arm spinners.
It is used for obtaining personal data and is usually exhaustive to include all categories or segmentation.
It used for ranking, rating or grading. It can show best to worst status or first to last preference. But distance between two ordinal scales is not the same. income level of poor, middle and rich class are like less than Rs.10,000, between Rs.11,000 to Rs.50,000 and 51,000 and above. The distances are 10,000, 39,000 and infinitve respectively.
It is evident that ordinal scale can rank some items in an order like less than or more but not “how much more”
It is more powerful than nominal and ordinal as it not only orders or ranks or rates but also shows exact distances in between. But it does not start from zero. If there is zero like zero temperature it is not natural but arbitrary as 0 degree does not mean no temperature. Likewise, year 0 in a forecast is the end of construction year.
This scale is used in addition or substraction of scale value to calculate mean, range, variance, standard deviation, correlation and regression.
Difference between interval and ordinal scale:
Ordinal scale only ranks but does not measure difference between the two ranks like “satisfactory” and “not-satisfactory”. Interval scale not only ranks but also give exact distance between them by assigning a value. Difference in temperature of 20 degree and 40 degree is 20 but 40 is not double hot than 20.
This scale can perform all functions. It can show all mathematical and geographical indicators. It is useful when exact figures are required in objective matters are required.
If a person is drawing a salary of Rs.20,000 and another Rs.40,000, it can be said that the latter is getting double the salary of the former.
FOUR SCALES COMPARED
Classification but no order, distance or origin
Classification but order but no distance or unique origion
Classificatiion, ordered and distance but no unique origin
Classification, order, distance and unique origin
Determinition of equality
Determinination of greater or lesser value
Determination of equlity of intervals or differences
Determination of equality of ratios
Ranks, Rating and Grade
Gener (male, female)
Doneness of meat, (well, medium well, medium rare, rare)
temperature in degrees
Age in years
Addition/substraction but no multiplication or division
Black & While
AAA, BBB, CCC
Can say no measurable value like zero sales
Levels, one-star & 4-star
Mean, range, variance, standard deviation
types of scalesClick thumbnail to view full-size
Rating and Ranking Scales.
Requires the respondent to estimate the magnitude of a quality that an object possesses. Scoring an object without making a direct comparison to another object.
- LIKERT SCALE
- SEMANTIC DIFFERENTIAL SCALE
- GRAPHIC SCALE
- Staple Scale
Requires that the respondents rank order a small number of activities, events or objects on the basis of overall preference or some characteristic of the stimulus.
- PAIRED COMPARISON
- FORCED CHOICE
- COMPARATIVE SCALE
RANKING AND RATINGClick thumbnail to view full-size
Validity and Reliability
In business research, all measurements should be both valid and reliable. Validity is relevancy and appropriateness of measuring instrument or scale. While we can judge the health of a child by use of weighing machine, we cannot use the same machine for checking his or her intelligence. The weighing machine is only valid for weighing. When we say is this machine reliable, we mean to say that it would give true measure whenever it is used.
VALIDITY AND RELIABILITYClick thumbnail to view full-size
RELIABILITY VALIDITY BIAS
More formally, Cook and Campbell (1979) define the validity as the "best available approximation to the truth or falsity of a given inference, proposition or conclusion."
Validity is the strength of our inferences and conclusion. If we cannot decide which instrument is valid for measuring our concept, we may ask the experts. If experts validate it, we can accept it on its face value. Or we go through the contents and find its validity. A training program for enhancing math skills in students should have plus, minus, multiplication and division aspects.
For testing validity of an instrument we can test it ability to predict. Opinion polls forecast outcome of the election. With necessary feedback, we can improve the questionnaire seeking opinion to predict as precisely as possible. SAT determines GPA in MBA. We can correlate SAT result and GPA result to see any association. If we do find, we can insist on having SAT for admission in MBA.
Similarly, an agency responsible for giving un-employment allowance should be able to make distinction among parasites and genuine job seekers. The person preparing the test method can be given 10 people, of which 3 are known parasites. If the test can point them out, it is valid test. Finally, a test for driving is valid which covers both driving skills, through a machine test, and sign recognition. If results from both tests are highly correlative or converge at the same conclusion, these are valid tests.
The instrument should be reliable. A weighing machine which gives different results in different attempts is not reliable. The measurement should stable and consistence. For stability, we can repeat the same test for a number of times. It should give more or less the same results of each participant. Or we may make two alternate forms of the same measure and administer simultaneously or with some delay. There should be high correlation between the two tests. In another method, a test based on 50 true or false questions can be split into two halves and it would be expected that results from the both would the same.
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