Chapters 1 & 2
Random assignment helps to strengthen causal inferences within an experiment by ruling out potential confounding variables otherwise introduced to an experiment due to individual differences in participants.
True or False
True
The mode is the only measure of central tendency that is appropriate to utilize for a variable measured with which scale of measurement?
Nominal Scale
In order to facilitate independent random sampling, sampling with _______ must be utilized.
Sampling with Replacement
For an ANOVA comparing three treatment conditions, what is stated by the alternative hypothesis (H1)?
At least one of the three population means is different from another population mean.
A Pearson correlation value (r) indicates the exact degree of accuracy in which a researcher can predict a participant’s score on a second variable from their score on a first variable.
(True or False)
False
The resulting value for the following notation is 7,054. Given the scores 9, 12, 13, 22, and 28, what is the correct summation notation?
a.Σ(X2 – 2)
b.Σ(X – 2)2
c.(ΣX)2 – 2
d. (X – 2)2
(ΣX)2 – 2
One sample with n = 4 scores has a mean of M = 12, and a second sample with n = 6 scores has a mean of M = 8. If the two samples are combined, what is the mean for the combined set of scores?
a. M = 8.4
b. M = 9.6
c. M = 9.8
d. M = 10
9.6
When a sample size from a population is n = 1, then the standard error will always equal the _____.
Standard Deviation
When comparing more than two condition means, why should an analysis of variance be used instead of multiple t tests (other than t tests can only be used for 2 groups)?
Using multiple t tests increases the risk of a Type I error.
A set of n = 15 pairs of scores (X and Y values) has SSX = 4, SSY = 25, and SP = 6. What is the Pearson correlation for these data?
r = 0.60
For the following distribution of quiz scores, if a score of X = 4 or lower is considered to be highly at risk for falling, how many individuals are highly at risk for falling?
X f
6 3
5 6
4 5
3 5
2 3
1 2
10 Individuals Failed
A sample of scores has a mean of 26, a median of 28, and a mode of 29. What is the most likely shape for the sample distribution?
Negatively Skewed Distribution
Under which circumstance can a very small treatment effect still be statistically significant?
If the sample size is very large.
A research study comparing three treatments with n = 5 in each treatment produces T1 = 22, T2 = 30, T3 = 23, with SS1 = 82, SS2 = 9, SS3 = 9, and ΣX2 = 444. For this research study, what is SStotal?
SStotal = 69
A researcher assesses self-esteem among college students at the beginning of the semester using a self-report questionnaire. Three months later, at the end of the semester, the researcher assesses self-esteem among the same sample of college students using the exact same self-report measure of self-esteem. The researcher determines that there is a significant positive relationship between self-esteem measured at the beginning and end of the college semester for the students sampled. This demonstrates how correlations can be used to demonstrate _____.
Reliability
In a frequency distribution graph, frequencies are presented on the _____ and the scores (categories) are listed on the _____.
a. X axis; Y axis
b. horizontal line; vertical line
c. Y axis; X axis
d. class interval; axis
In a frequency distribution graph, frequencies are presented on the Y axis and the scores (categories) are listed on the X axis.
It is only appropriate and possible to calculate the variance and standard deviation as measures of variability for variables measured using a(n) _____ or _____ scales of measurement.
Interval Scale or Ratio Scale
If random samples, each with n = 16 scores, are selected from a normal population with µ = 100 and σ = 20, how much difference, on average, should there be between a sample mean and the population mean?
a. 16 points
b. 3 points
c. 4 points
d. 5 points
5 points
An analysis of variance is used to evaluate the mean differences for a research study comparing four conditions with a separate sample of n = 8 in each condition. If the data produce an F-ratio of F = 4.60, which of the following is the correct statistical decision?
(Compare with alpha .05 and alpha .01)
Reject the null hypothesis with either α = 0.05 or α = 0.01.
A set of n = 25 pairs of scores (X and Y values) in a research study has a Pearson correlation of r = 0.55. What percentage of the variance for the Y scores is predicted by its relationship with X?
r2 = 30.25%
Barbara is a psychologist who measures relationship satisfaction among couples by observing non-verbal behavior, defined by smiling and mimicking partner actions. In this example, smiling and mimicking partner actions are _____.
a. discrete variables
b. operational definitions
c. constructs
d. continuous variables
Operational Definitions
Which of the following characteristics tends to increase the likelihood that a clear difference between two sample means is detected statistically?
a. a small difference between sample means
b. large variances within each sample
c. small variances within each sample
d. small sample sizes
Small variances within each sample.
Larry wants to do everything possible to be in a position to detect that a treatment he has designed is effective given that it is actually effective. Which of the following should he do?
Select the 2 that apply.
a. increase the sample size
b. use an alpha (α) of 0.01 instead of 0.05
c. decrease the population standard deviation
d. use an alpha (α) of 0.05 instead of 0.01
Increase the Sample Size and Use an Alpha of .05 instead of .01
The following table shows the results of an analysis of variance comparing three treatment conditions with a sample of n = 7 participants in each condition. Note that several values are missing in the table. What is the value of F?
Source SS df MS
Between 20 xx xx F = xx
Within xx xx 2
Total xx xx
F = 5
Which correlation should be used to measure the relationship between fans of basketball teams (Kings fans vs Lakers fans) and level of integrity for a sports enthusiast?
Point-biserial Correlation