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Measurement scales

Measurement scales presentation

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Measurement scales

  2. 2. What are Variables and Measurements Variables: Characteristics that can take on different values for different members of a group. For example height Measurements: “Assignment of numbers to Characteristics (variables) of objects, persons or events.”
  3. 3. In statisticsand quantitative researchmethodology, levels of measurementare developed by the psychologist Stanley Smith Stevens.
  4. 4. •Researchconclusionsareonlygoodwhenthemeasurementsareaccurateonwhichtheyarebased. •Themoreprecise,sensitivethemethodofmeasurement, thebetteraretheresults. IMPORTANCE OF MEASUREMENT
  5. 5. Stevens(1946)classifiedvariablesintofourlevels.Thesearereferredtoaslevelofmeasurement,orlevelsofdata. 1.Nominal 2.Ordinal 3.IntervalScale 4.RatioScale Nominal Interval Ratio Attributes are only named; weakest Attributes can be ordered Distance is meaningful Absolute zero Ordinal
  6. 6. Nominal scale Thenominaltypescale,sometimesalsocalledthequalitativetypethatdifferentiatesbetweenitemsorsubjectsonlyonthebasistheirnamesorcategoriesorqualities. Examples includegender, nationality, language, style, and biological species.
  7. 7. A nominal scale represents lower level of measurement. Such scales classifies persons or objects in to two or more categories. Nominal scale
  8. 8. •Example: Country of Origin •1 = United States3 = Canada •2 = Mexico4 = Other Assignment of numbers to the categories has no mathematical meaning like However, in this case, it is important to keep in mind that the numbers do not have intrinsic meaning Nominal scale
  9. 9. Ordinal scale An ordinal scale not only classifies subjects but also ranks them in terms of the degree to which they possess a characteristics of interest. An ordinal scale indicates relative position. Ordinal scale can determine whether an object has more or less of a characteristic than some other object. The exact measurement is not available like student A is taller than student B but their actual heights are not available. It permits the researcher to rank or order the respondents or their responses
  10. 10. Example of an ordinal scale: The result of a horse race, which says only which horses arrived first, second, or third but include no information about race times. Common example of ordinal scale include quality ranking, socioeconomics classes,and occupational status. Ordinal scale
  11. 11. Interval scales indicate order and also the distance in the order. Zero point on the interval scale is arbitrary zero, it does not means the complete absence of anything
  12. 12. Examples Temperature Scale in Fahrenheit. The difference in temperature between 20 degrees F and 25 degrees F is the same as the difference between 76 degrees F and 81 degrees F interval scale
  13. 13. Interval scales allow comparisons of the differences of magnitude (e.g. of attitudes)but do not allow determinations of the actual strength of the magnitude. interval scale
  14. 14. This is the highest level of measurement and has the properties of other three levels. This scale has a unique or fixed beginning or true zero point. (complete absence of the phenomenon being measured) Ratio scale
  15. 15. For example heart beats per minute has a very natural zero point. Zero means no heart beats. Weight (in grams) is also a ratio variable. Again, the zero value is meaningful, zero grams means the absence of weight. Ratio scale
  16. 16. Ratio scale allow comparisons of the differences of magnitude (e.g. of attitudes) as well as determinations of the actual strength of the magnitude. Ratio scale
  17. 17. Reliability and Validity For a research study to be accurate, its findings must be both reliable and valid. Criterion for the selection of instruments Criteria of selecting instruments include Is our measure valid? Is our measure reliable?
  18. 18. Reliability Research means that the findings would be consistently the same if the study were done over again Validity A valid measure is one that provides the information that it was intended to provide. The purpose of a thermometer, for example, is to provide information on the temperature, and if it works correctly, it is a valid thermometer. Criterion for the selection of instruments
  19. 19. Thank you