The testretest method is one way of establishing the reliabi

The test-retest method is one way of establishing the reliability of a test. The test is administered, and then, at a later date, the same test is re-administered to the same individuals. The correlation coefficient is computed between the two sets of scores. The following test scores were obtained in a test-retest situation. (Give your answers correct to two decimal places.)

(a) Find r.

(b) Set a 95% confidence interval for .

First Score	72	67	91	71	96	69	71	62	77	82
Second Score	68	85	65	57	61	78	89	75	82	61

The value of the correlation coefficient r is calculated in the excel

Now, R = -0.52657

The bounds are set as:

Lower bound =

[ (1+R) - (1-R)e^{2z / sqrt(n-3)} ] / [ (1+R) + (1-R)e^{2z / sqrt(n-3)} ]

= -2.4421

Upper Bound

[ (1+R) - (1-R)e^{-2z / sqrt(n-3)} ] / [ (1+R) + (1-R)e^{-2z / sqrt(n-3)} ]

= 0.15418

Hope this helps. Ask if you have any queries.

First Score	Second Score
72	68
67	85	Correlation	-0.52657
91	65
71	57
96	61
69	78
71	89
62	75
77	82
82	61

The test-retest method is one way of establishing the reliability of a test. The test is administered, and then, at a later date, the same test is re-administer

The testretest method is one way of establishing the reliabi

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