Exam 1

  1. Metainformation

    Tag Value
    fileReliability_eur-reliability-115-en_eur-reliability-115-en
    nameeur-reliability-115-en
    sectionReliability/Analysis/Cronbach's alpha
    typenum
    solution0.355
    tolerance0
    TypeCalculation
    ProgramCalculator
    LanguageEnglish
    LevelStatistical Literacy

    Question

    A test that measures assertiveness is administered both before and after an assertiveness training. The variance in the pre‐test is 8 and the reliability is .75. The post‐test has a variance of 7 and the reliability is .80. The correlation between the pre‐ and post‐test scores is .65. Calculate the reliability of the differences scores.

    Rd=SXo2×RXX+SYo2×RYY−2×rXoYo×SXo×SYoSXO2+SYO2−2×rXoYo×SXo×SYoR_d = \frac{S^2_{Xo} \times R_{XX} + S^2_{Yo} \times R_{YY}-2\times r_{XoYo}\times\ S_{Xo} \times S_{Yo}}{S^2_{XO} + S^2_{YO} - 2\times r_{XoYo}\times\ S_{Xo} \times S_{Yo}}


    Solution

    To calculate the reliability of the differences scores, one has to use the beforementioned formula, giving us the following outcome: Rd=8×.75+7×.80−2×.65×8×78+7−2×.65×8×7=1.875.27=.355R_d = \frac{8 \times .75+7\times.80-2\times.65\times\sqrt{8\times7}}{8+7-2\times.65\times \sqrt{8\times7}} = \frac{1.87}{5.27} = .355