Quiz (Chapter 3)


Bivariate Correlation

The Key Concept Behind Correlation: Relationship

  1. (T/F) The concept of "relationship" cannot be investigated if we measure each person in a group one time only on a single variable.
  2. What kind of relationship exists among the math and science quiz scores shown below:
    1. high-high, low-low
    2. high-low, low-high
    3. little systematic tendency one way or the other
     
    Person
    Math
    Science
    Will
    7
    5
    Jill
    9
    3
    Bill
    8
    4

  3. Add 10 points to each person's math score in the previous question and then answer it again.

Scatter Diagrams
  1. If a scatter diagram is used to show how 20 people score on 2 variables, how many axes will there be in the scatter diagram?  How many dots in the scatter diagram?
  2. If a "high-low, low-high" relationship exists between two variables, the "path" of dots in the scatter showing this relationship will extend from:
    1. upper-right to lower-left
    2. upper-left to lower right
  3. Where would you be located in a scatter diagram if you've got the top scores and its a "high-high, low-low" relationship?

The Correlation Coefficient
  1. Which of the following correlations is "highest"?
    1. -.35
    2. +.80
    3. -.05
    4. +.65
    5. -.95
  2. (T/F) Since a correlation of +1 is "perfect," a correlation of -1 is as "imperfect" as can be.
  3. "Positive" is to "negative" as "direct" is to "_______."
  4. What lower-case letter is generally used to represent a correlation coefficient?
  5. (T/F) When used in reference to correlation coefficients, the adjectives "modest" and "moderate" mean the same thing.
  6. (T/F) If r is +1.00, the means of the 2 variables will necessarily be identical to each other.

The Correlation Matrix
  1. Which two variables had the lowest correlation in Excerpt 3.10?
  2. If all possible bivariate ("pairwise") correlations are computed among 10 variables, there will be at least ___ (how many) correlation coefficients in the correlation matrix.
  3. If a correlation matrix has 4 rows & 4 columns, then there were ___ or ___ variables to start with.

Different Kinds of Correlational Procedures
  1. What kind of measurement scale leads to rank-ordered data?
  2. Which term--dichotomous or nominal--covers the other (and covers other things too)?
  3. If people are called "tall" if they're over 5'6" (and "short" if they're not), is this a true dichotomy?
  4. What symbols are used to designate Pearson's correlation and Spearman's correlation?
  5. Which correlational procedure handles data sets having ties better than does Spearman's?
  6. What do the letters bis stand for in the notation rbis?  What about the letters pb in the notation rpb?
  7. If we were to correlate hand preference (left vs. right) with gender (male vs. female), which correlational procedure would be most appropriate:  phi or tetrachoric?
  8. What letter of the alphabet is used to denote Cramer's correlational procedure?

Warnings About Correlation
  1. If the correlation is greater than .90, can we assume that a causal relationship exists?
  2. In Excerpt 3.9, the coefficient of determination for ES and AG (for the paper-and-pencil version) is equal to __ .
  3. In Excerpt 3.8, approximately what % of the variability in Spelling scores was explained by variability among the Social Studies scores?
  4. (T/F) Depending on their location, outliers can either increase or decrease the size of r.
  5. Does the term "linear" apply to these 8 pairs of math (M) and geography (G) scores?

  6.  
    Name
    M
    G
    Joe
    2
    1
    Sam
    1
    2
    Sue
    3
    Ann
    2
    Bob
    4
    3
    Dan
    3
    4
    Eve
    5
    4
    Pam
    4
    5
     
  7. Two variables are considered to be "independent" if the correlation of scores on the variables turns out to be close to __ .
  8. (T/F) The decision as to how an r should be labeled (e.g., as "high" or "moderate" or "low") is quite subjective, and different researchers might use different labels even though their correlation coefficients are exactly the same size.

A Few Extra Questions that are Supposed to be More Challenging
  1. (T/F) In Excerpt 3.7, the correlation between Family Support and Avoidance/Detachment suggests that these two factors were not at all independent of each other.
  2. Look at Excerpt 3.1. If each county's "Votes Cast" percentage had turned out exactly 10 percentage points higher than its "Voters Registered" percentage, what two terms could we use to describe the relationship between the two sets of percentages?
  3. (T/F) Given 8 totally different scores, it's possible to create a "high-high, low-low" situation by (a) positioning the top 4 scores in the X column & (b) positioning the lowest 4 scores in the Y column.

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Schuyler W. Huck
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