If a Test That Has Reliability R Is Lengthened by a Factor

Multiple Choice

If a test that has reliability r is lengthened by a factor , the reliability R of the new test is given by ​ ​
​If the reliability is r = 0.6, the equation becomes . When the test length is unchanged, the reliability r = R(1) = 0.6. If the length of the test is doubled, the reliability r = R(2) . What percent improvement is there in the reliability when the test length is doubled?
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A) 20.0%
B) 25.0%
C) 80.0%
D) 75.0%
E) 15.0%