Download a. always equal to the correlation coefficient

Psych 315 Spring 2003 Exam 3: Practice
Multiple choice questions (4 points each):
1. The slope of the regression/prediction line (using the least squares
criterion) is
a. always equal to the correlation coefficient
b. equal to the correlation coefficient if r = 1
c. equal to the correlation coefficient if the x and y variables are
in standardized form
d. not related to the correlation coefficient
2. The least squares method is the criterion of best fit most commonly used
In linear regression. This method is based on
a. minimizing the errors made in prediction by the regression line
b. minimizing the correlation coefficient
c. maximizing the number of points that the regression line passes
through
d. minimizing the sum of squared errors made by the regression line
3. The regression/prediction line (using the least squares criterion) is
a. very resistant to effects of outliers
b. very sensitive to the location of outliers
c. sensitive to the location of outliers only if the slope is negative
d. sensitive to the location of outliers only if the slope is positive
4. Which of the following statistics can be used to get an idea of how “good”
The regression line is at predicting values of y:
a. the regression constants, a (intercept) and b (slope)
b. r (the correlation coefficient) and b (slope)
c. the mean of x and the mean of y
d. r (the correlation coefficient) and sxy (the standard error of estimate)
5. The binomial distribution and the normal distribution are both
a. examples of distributions that can be regarded as sampling
distributions
b. probability distributions
c. theoretical distributions
d. all of the above
6. The simple form of the multiplication rule is appropriate to determine
a. the joint probability of two mutually exclusive and dependent events
b. the joint probability of two independent events
c. the joint probability of two dependent events
d. the probability of one OR the other mutually exclusive events
7. Two events are not independent when
a. the outcome of one event has some influence on the outcome of the
other event
b. the outcome of one event is not related to the outcome of the other
event
c. the two events cannot both happen
d. the two events are not mutually exclusive
8. Sampling with replacement and sampling without replacement yield
different distributions of sample means. Under what circumstance is it
possible to use the sampling distribution of the mean obtained by sampling
with replacement when the actual sampling is accomplished without
replacement?
a. when the sample size is very large
b. when the population size is very large
c. when the population size is very small
d. when the population size is large relative to the size of the sample
9. A random sampling distribution of the mean is normally distributed when
a. sample size is small relative to the size of the population
b. the population is normally distributed
c. the sample size is at least 25 or 30
d. both b and c
10. The single sample z test and the single sample t test differ in:
a. the level selected the researcher’s hypothesis is about population means
b. the number of tails in the test
c. whether the standard error is known or estimated
d. the numerator of the test statistic (the test statistic is the z or the t)
Short answer questions:
1. Why is a two-tailed test preferred for scientific questions?
2. Why is it difficult (if not impossible) to determine the exact probability of
obtaining a sample mean (or one even more extreme in either direction) from a ttable? HINT: what is it about the difference in the z distribution and the t
distribution ?
3. Why must the population sampled from be normally distributed or sample size
be sufficiently large for the z test to be appropriate?