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Homework Help: This is actually

  1. Jul 18, 2010 #1
    1. The problem statement, all variables and given/known data

    ... a Statistics problem ...

    2. Relevant equations

    .... but it involves ...

    3. The attempt at a solution

    ... enough math that I think it will fly here.

    In a study of the stability of IQ scores, a large group of individuals is tested once at age 18 and again at age 35. The following results are obtained

    age 18: average score ≈100, SD ≈ 15
    age 35: average score ≈ 100, SD ≈ 15, r ≈ 0.80

    (a) Estimate the average score at age 35 for all the individuals who scored 115 at age 18
    (b) Predict the score at age 35 for an individual who scored 115 at age 19

    So ... I know to use the regression line y = (SDy / SDx) * r * x + b , to estimate with an accuracy of +/- √(1-r2) * SDy, but it is that what is being asked in (a) or is it being asked in (b)? And then what's the other asking? What's the difference "estimate" and "predict", "individual" and "individuals", in terms of this problem
  2. jcsd
  3. Jul 24, 2010 #2
    What is r in this problem?
  4. Jul 24, 2010 #3
    Isn't the difference between (a) and (b) just that (a) has x=18 while (b) has x=19? Or maybe I'm overlooking something.
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