A correlation coefficient measures
the degree of linear relationship between two variables
the magnitude of the difference between two variables
the estimated effect size between two variables
the degree of relationship between two variables
A negative correlation means that
a high score on one variable is usually associated with a low
score on the other
A positive correlation means that
a high score on one variable is usually associated with a high
score on the other
none of the above
If the points in a scatter diagram generally tend from upper
left to lower right, you would conclude that the correlation was
probably
negative
Which of the following values for a correlation coefficient
would indicate the strongest degree of relationship?
a.
-.69
b.
-.35
C.
+.03
d.
+.59
If ΣZxZy = 0, r is
zero
If ΣZxZy= 4 and n = 8,
r is equal to:
a. -.50
b. 0
C.
+.50
d. impossible to
determine from the information provided
If Y' = Ȳ at all levels of X, the correlation coefficient would
probably be
zero
Exhibit 31
Suppose you are
interested in marksmanship. You have 50 army enlistees fire a
shotgun at 100 targets each, and then have the same 50 individuals
fire a rifle at 100 targets each. Thus, each individual gets a
shotgun score (number of hits out of 100 targets) and a rifle score
(number of hits out of 100 targets). You compute the Pearson
product moment correlation coefficient for these subjects and wish
to test whether it is significantly different from zero.
Refer to Exhibit 31. The number of degrees of freedom for this
test is
a. 100
99
98
50
48
Two factors that can lower the correlation coefficient
are
The nonlinearity of a relationship, restriction of range
Sample size, restriction of range
and
The sample size of variable 1, the sample size of variable
2
What does a correlation of .67 between lack of sleep and
illness imply?
Lack of sleep and illness are highly related.
Linear regression
determines the best straight line through a data set
is used to predict Y from X
both a. and b.
none of the above
The error of prediction for the ith individual is given by
ei= Yi - Y'i
The least squares criterion for the regression line states that
the best regression line produces the smallest sum of squared
errors of prediction
the variance of the X variable must be less than the
variance of the Y variable
the variance of the Y variable must be less than the variance of
the X variable
the best regression line has the steepest slope