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Measurement

measurement, error, reliability, validity

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Measurement

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  1. Measurement EDRS 6301 Summer 2001 Dr. Kielborn

  2. Measurement • All measures contain error • Random error leads to unreliability • Systematic error leads to invalidity • True Score = Obtained Score + Random Error

  3. A true score is the real and unchanging measure of the human characteristic The error score is a positive or negative value that results from uncontrolled and unrealized variability in the measurement True Scores and Error Scores

  4. Error • Error can be the result of the way we observe or test the individual • Observational (difficulty, broad test with few samples matching each concept; items unclear to the participant) • Procedural (inconsistent administration, recording, scoring or interpretation)

  5. Error continued • Subject - (Individuals performing differently; reaction of participant to instrument or experiment)

  6. Reliability • Reliability is consistency in measurement • Consistency is specific to the group being assessed • If there is consistency, there is confidence in the results

  7. Reliability • The consistency of measurement • It is the extent to which observations/ experimental design can be replicated by another independent researcher • How consistently a data collection process measures whatever it measures

  8. Faulty items and observations (tricky, ambiguous, or confusing) questions or format Excessively difficult elements of the data collection process (participants guess) Excessively easy elements of the data collection process Inadequate number of observations or items Sources of Unreliability

  9. Accidentally focusing on multiple outcomes (all or most test items or questions in an interview/survey refer to the same characteristic) Faulty scoring Characteristics of the respondents (inability to concentrate, mood) Faulty administration (room may be hot or cold or full of distractions) Sources of Unreliability

  10. Validity • Does it measure what we think it is measuring? • High validity - high amount of accuracy

  11. Validity • Establish rapport • Minimize disruptions • Use unobtrusive methods for recording data • Triangulation - confirming results through more than one data source

  12. Internal validity • The extent to which the results of a study are supported by the methodology. A well-controlled study is said to have high internal validity and “believable” conclusions.

  13. History - An event occurring between pre and post tests Maturation - A change that occurs because a participant has grown older or gained experience Instrumentation - A change that occurs because the testing procedures are unreliable or have altered unintentionally Threats to Internal Validity

  14. Testing - A change that occurs because the test has sensitized the participants to the nature of the research Regression - The tendency of a very low score or a very high score to move toward the mean Threats to Internal Validity

  15. References • Marshall, J. (2001). Assessment for educational improvement workshop, UWG, Carrollton, GA, June 16, 2001. • Schloss, P.J., & Smith, M.A. (1999) Conducting research. Upper Saddle River, NJ: Merrill. • Vockell, E.L., & Asher, J.W. (1995) Educational Research (2nd Ed.). Upper Saddle River, NJ: Merrill.

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