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Do I perform a Z-test?

  1. Feb 4, 2008 #1
    Hi all:

    1. The problem statement, all variables and given/known data

    Sample 1: M = 62.77, SD = 6.52
    Sample 2: M = 72.91, SD = 6.22
    Sample 3: M = 74.61, SD = 6.60

    2. Relevant equations

    Now if I wanted to calculate what proportion of students in each population would be expected to receive a grade <50 and receive a grade >80, would I perform a Z-test using Z = (X-mu)/Sd


    3. The attempt at a solution

    For example, in sample 1:

    (For <50)
    Z = 50 - 62.77 / 6.52 = -1.959, P = 0.0202 (according to Z-table)
    So, .5 - .0202 = .4798 = approximately 48% of the students in the first population would receive a score <50...is that correct?

    (For >80)
    Z = 80 - 62.77 / 6.52 = 2.65, P = 0.4965(according to Z-table)
    So, .5 - .4965 = .0035 = approximately .35% of the students in the first population would receive a score >80...?
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
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