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Test-Retest Reliability (ICC) and Day to Day Variation

Test-Retest Reliability (ICC) and Day to Day Variation. Consistency of Measurements. Reliability refers to the consistency of a test or measurement. A test cannot be considered valid if it is not reliable. You should know the day to day variation in your dependent variable.

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Test-Retest Reliability (ICC) and Day to Day Variation

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  1. Test-Retest Reliability (ICC)and Day to Day Variation

  2. Consistency of Measurements • Reliability refers to the consistency of a test or measurement. • A test cannot be considered valid if it is not reliable. • You should know the day to day variation in your dependent variable. • How much does 1RM bench press change from day to day? • How much does VO2 max change from day to day?

  3. The 1RM squat strength was measured on 8 subjects on two separate days. In this experiment we want to measure the reliability of our measurements. Here is the day to day variation in 1RM bench press strength. Test-Retest Reliability In this experiment, we plan to average trials, so we will use Averaged Measures ICC.

  4. Enter the between day variables.

  5. Click Statistics

  6. Click OK to run

  7. SPSS Output

  8. There is no difference between trials F(1,7) = .530, p = .49 If there is a difference between trials you may have a learning effect or a fatigue effect and you must modify your methods to control for learning and/or fatigue.

  9. ICC = .973 [High Degree of Reliability] Using Mixed Model, Type Consistency, Averaged Measures.

  10. Day to Day Variation • If you train subjects for 8 weeks and they improve their strength by 2.8 Kg have you actually done anything? • Is the program effective? • Here is the day to day variation in 1RM bench press strength.

  11. Manuscript Methods & Results Sections METHODS Measurement of Reliability Prior to initiating the study, 8 subjects (not in the experiment), participated in a test-retest assessment of measurement reliability. One RM bench press strength was measured on two separate days for subjects in the reliability study. Reproducibility of bench press strength was analyzed using SPSS (16.0 for Windows) to compute the intraclass correlation coefficient (ICC) using a two factor mixed effects model and type consistency (McGraw and Wong, 1996; Shrout and Fleiss, 1979). RESULTS A high degree of reliability was found between bench press strength measurements the average measure ICC was .973 with a 95% confidence interval from .864 - .995.The mean between day variation for 1RM strength was 2.75±10.7 Kg. REFERENCES McGraw KO and Wong SP. Forming inferences about some intraclass correlation coefficients. Psychological Methods 1: 30-46, 1996. Shrout PE and Fleiss JL. Intraclass correlations: Uses in assessing reliability. Psychol Bull86: 420-428, 1979.

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