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Homework Help: Statistics help - Scatter plot, regression

  1. Jun 22, 2011 #1
    Statistics help -- Scatter plot, regression

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

    Consider the following data set for ten first grade students; the variables are the number of minutes spent learning a list of spelling words and the number wrong on the spelling test. [15 points total]

    (supposed to be a chart)
    MINUTES 25 28 30 31 31 35 36 38 40 50
    WRONG 12 10 8 1 6 4 4 3 2 1

    a. Describe the scatter plot: form, direction, and strength. [3 points]
    b. Determine the value of the correlation coefficient.
    c. Determine the value of the coefficient of determination (state as a percent).
    d. Find the slope of the best fitting regression line for predicting number wrong.
    e. Find the intercept of this regression line.
    f. Present the equation of this best fitting regression line.
    g. If another student now studies the list for 32 minutes, use the equation to predict his number wrong.
    h. If that student’s actual number wrong is 8, determine the residual associated with this prediction.
    i. Plot the regression line on your scatterplot. (submit this plot)
    j. Are there any outliers? If so, give the coordinates.
    k. Are there any influential points? If so, give the coordinates.
    l. Suppose another student studies the list for 60 minutes. Predict his number wrong.
    m. Comment on this prediction.

    2. Relevant equations
    y = mx+b

    3. The attempt at a solution

    a.strong; positive
    b. 4.65
    c. 68%
    d. ?
    e. 30
    f. 28
    g. ?
    h. ?
    I don't understand how to do this, please help:(
  2. jcsd
  3. Jun 22, 2011 #2


    User Avatar

    Staff: Mentor

    Re: Statistics help -- Scatter plot, regression

    Welcome to the PF.

    Can you please show us your work on the answers that you were able to calculate? That will help us a lot. Thanks.
  4. Jun 23, 2011 #3
    Re: Statistics help -- Scatter plot, regression

    my work for this problem is..

    b) -.4096 = (3.8137/7.1678) r
    r = -.7698

    c) (-.7698)^2

    d) y= -.4096x +19.1903

    e) m=-.4096

    f) y = -.4096x = 19.1903

    g) y = -.4096 (32) + 19.1903

    h) 8 - 6.0831 = 1.9169

    i) ?

    j) (31,1)

    k) graphed

    l) y= -.4096(60) + 19.1903 = -5.3857

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