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  5.7 Reliability of measurement

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  • the degree to which the test yields the same results when given on two or more different occasions or by the different examiners to the same group of individuals

  • determined statistically by correlation, t-tests, or regressions

Using a regression between the first and second measure, good reliability would exhibit the following characteristics:

Subjects  Data Set 1  Data Set 2
1 32.1 31.9
2 33.1 33.1
3 34.2 33.9
4 35.2 35.1
5 36.1 35.8
6 33.1 33.2
7 36.9 37.1
8 35.1 34.9
9 36.3 36.2
10 32.3 31.8
11 34.4 34.1
12 33.2 32.9
13 35.1 35.3
14 37.4 36.7
15 34.3 34.1
16 37.9 37.9
17 33.9 33.2
18 34.8 34.8
19 38.2 38.2
20 36.3 35.8
Mean 34.995 34.8

Using the expression y = mx + c for regression

1.slope of 45 degrees (slope = 1)

2.constant of zero

3.correlation coefficient > 0.90 (?)

4.Significance level? 0.01, 0.05?

Correlation Data Set 1 Data Set 2
Data Set 1 1.000000 0.990076
Data Set 2 0.990076 1.000000

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