Other's On-Line Resources (Chapter 3)

 

Scatter Diagrams
  • Description:
    You'll see 4 scatter diagrams from a real study involving people who were measured in terms of two variables: isometric strength and job performance.

  • What to Do:
    1. Click on the colored title of this on-line resource: "Scatter Diagrams."
    2. Examine the 4 scatter diagrams, carefully noting (in each case) what 2 variables were involved.
    3. Try to correctly answer, on your first try, the multiple-choice question that's located immediately after the final scatter diagram

  • Sky Huck's Puzzle Question:
    The 2nd of the 4 scatter diagrams involves the variables "SIMS" and "ARM." Do you think the correlation would be higher or lower if all data points were to be deleted except those that involve positive SIM scores combined with ARM scores greater than 80?
     
Guessing Correlations
  • Description:
    In this interactive on-line resource, you'll be given several scatter diagrams and are asked to guess the size of the correlation coefficient for each set of data points. Your answers are scored for each set of 4 scatter diagrams you examine, with a cumulative score displayed if you look at more than 4 sets of data.

  • What to Do:
    1. Click on the colored title of this on-line resource: "Guessing Correlations."
    2. Scroll down to the section called "Step by Step Instructions."
    3. Look at the scatter diagram and then choose one of the 5 possible values for r shown beneath the scatter diagram.
    4. Click on the "New Data" button to see a new scatter diagram with a new set of possible values for r.
    5. Repeat steps 3 and 4.

  • Sky Huck's Puzzle Question:
    Select one of this site's scatter diagrams, and determine which of the 5 options has the correct value of r. Next, imagine that each dot's score along the abscissa (i.e., the horizontal axis) is cut in half. Likewise, imagine that each dot's score along the ordinate (i.e., the vertical axis) is cut in half. Now, if the correlation were to be computed for the revised data, would r be half as large as it was for the original data?
     
Pearson's Product-Moment Correlation
  • Description:
    In this interactive on-line resource, you'll first enter pairs of scores on 2 variables and then quickly be able to see the resulting value of r for the data you entered. (The scores you enter can be "real," in the sense that they come from a set of people, animals, or things actually measured by you or someone else; or, your scores can be "artificial," in the sense that they are created by you solely for the purpose of "playing" with data to see how changes in data influence the size of Pearson's r.)

  • What to Do:
    1. Click on the colored title of this on-line resource: "Pearson's Product-Moment Correlation."
    2. In the small box that appears on your screen, enter the number of pairs of scores in your data set. (The word "undefined" that initially appears in the small box will be replaced by your value for "n" once you type in the number of pairs of scores you have.)
    3. On the next screen that appears, scroll down until you get to a section called "Data Entry." In that section, enter your paired scores in the X and Y columns under the heading "Data cells." (Do not put anything in the column called "Residuals" or in the box called "Import/Export Box.")
    4. Click on the "Calculate" button positioned beneath the Y scores you just entered.
    5. Scroll down slightly, just past where you're provided with the standard deviations for your X and Y scores. Look to see (a) the numerical value of the correlation coefficient (r) for your data and (b) the coefficient of determination (r2).

  • Sky Huck's Puzzle Question:
    Using these 10 whole numbers [1, 2, 3, 4, 5, 6, 7, 8, 9, and 10], create 5 pairs of scores in an effort to generate the largest possible positive value of r. There are 2 little rules for this game: (1) each of the 10 numbers must be used once and only once as you go about the task of creating your 5 pairs of numbers, and (2) the 2 numbers that form any pair cannot together add up to more than 14. If you accept this little challenge, can you obtain an r equal to +.90? Can you obtain an r that's higher than this?
     
Spearman's Rho
  • Description:
    This interactive on-line resource will compute, for the data you enter, Spearman's rank-order correlation coefficient. You have the option of entering your data in the form of ranks or in the form of raw scores. If you enter raw scores, they will be converted into ranks for you. (The raw scores or ranks you enter can be "real," in the sense that they come from a set of people, animals, or things actually measured by you or someone else; or, your data can be "artificial," in the sense that they are created by you solely for the purpose of "playing" with data to see how changes in data influence the size of rs.)

  • What to Do:
    1. Click on the colored title of this on-line resource: "Spearman's Rho."
    2. In the small box that appears on your screen, enter the number of pairs of scores in your data set. (The word "undefined" that initially appears in the small box will be replaced by your value for "n" once you type in the number of pairs of scores you have.)
    3. On the next screen that appears, scroll down until you get to a section called "Data Entry." In that section, enter your data in one of these two ways:
      • If you have data in the form of unranked raw scores, enter your data in the two columns labeled "Raw data for X and Y." The top numbers in those columns would be your 1st pair of scores, the 2nd numbers down would be your 2nd pair of scores, etc.
      • If your data are in the form of ranks, enter those ranks in the two columns labeled "Ranks for X and Y." The top numbers in those columns would be your 1st pair of ranks, the 2nd numbers down would be your 2nd pair of ranks, etc.
    4. Click on the "Calculate" button directly beneath the data you just entered.
    5. Just below the "Calculate" button, look at the numbers displayed in the "n" and "rs" windows. The first of these number should match up with the number of pairs of scores you had. The number in the "rs" window is the value for Spearman's rho.

  • Sky Huck's Puzzle Question:
    First set n equal to 5. Next, consider yourself free to enter the numbers 1 through 5 in any order you'd like in the two columns labeled "Ranks for X" and "Ranks for Y." And now here comes your two-fold task:
    1. Can you arrange the ranks such that rs turns out equal to +.50?
    2. Can you arrange the ranks such that rs turns out equal to +.75?
       

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Schuyler W. Huck
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