PSY 311 Statistics
In a 2-factor experiment with 2 levels of factor A and 2 levels of factor B, three of the treatment means are essentially identical and one is substantially different from the others. What result(s) would be produced by this pattern?
1, 24
A repeated measures study and an independent-measures study both produced a t statistic with df= 10. How many individuals participated in each study?
11 for repeated-measures, and 12 for independent-measures
A set of X and Y scores has SSX = 10, SSY = 20, and SP = 8. What is the slope for the regression equation?
8/10
If a treatment has a very small effect, what is a likely outcome for a hypothesis test evaluating the treatment?
A Type II error
A researcher plans to conduct a research study comparing two treatment conditions with a total of 20 participants. which of the following design would produce 20 scores in each treatment?
A repeated-measures design
Which of the following sets of sample data would produce the largest value for an independent-measures t statistic? Assume that n = 10 for all samples.
A sample mean difference of 10 points with SS = 10 for both samples.
For an ANOVA comparing 3 treatment conditions, what is stated by the alternative hypothesis (H1)?
At least one of the 3 populations means is different from another mean.
In a repeated-measures ANOVA, the variability within treatments is divided into two components. What are they?
Between subjects and error
In an analysis of variance, differences caused by treatment effects contribute to which of the following variance?
Between-treatments variance but not within-treatment variance
Which of the following situations would a repeated-measures research design be appropriate?
Comparing pain tolerance with and without acupuncture needles
What research situations would be most likely to use an independent-measures design?
Comparing the mathematics skill for 9th grade boys vs. 9th grade girls
For an experiment comparing more than two treatment conditions, why should you use analysis of variance rather than separate t tests?
Conducting several t tests would inflate the risk of a Type I error.
For the independent-measures t statistic, what is the effect of increasing the sample variances?
Decrease the likelihood of rejecting H0 and decrease measures of effect size.
What accurately describes the effect of increasing the sample size?
Decreases the standard erro and has no effect on the risk of Type I error
Scatter plot for a set of X and Y values shows the data points clustered in a nearly perfect circle. For these data, what is the most likely value for the Pearson correlation?
Either positive or negative near 0
If an analysis of variance is used for the following data, what would be the effect of changing the value of M2 to 20? Sample Data M1 = 10 M2 = 15 SS1 = 90 SS2 = 70
Increase SSbetween and increase the size of F-ratio
Which combination of factors would definitely increase the width of a confidence interval?
Increase the sample mean and increase the percentage of confidence
Assuming that other factors are held constant, which of the following would tend to increase the likelihood of rejecting the null hypothesis?
Increase the sample mean difference
Which of the following will NOT increase the width of a confidence interval?
Increase the sample mean from MD = 2 to MD = 4
Which of the following would have no effect on the width of a confidence interval?
Increasing the sample mean
In the F-ratio for a repeated-measures ANOVA, what happens to variability caused by individual differences?
Is automatically eliminated from the numerator but must be computed and subtracted out of the denominator.
The Pearson and the Spearman correlations are both computed for the same set of data. If the Pearson correlation is r = +1.00, then what can you conclude about the Spearman correlation?
It will be positive.
In general, if the variance of the difference scores increases, then what will happen to the value of the t statistic?
It will decrease (move toward 0 at the center of the distribution).
If the mean and variance are computed for each sample in an independent-measures, 2-factor experiment, which of the following types of sample data will tend to produce large F-ratios for the 2-factor ANOVA?
Large differences between sample means and small sample variances
What would the scatter plot show for data that produce a pearson correlation of r = +0.88?
Points clustered close to a line that slopes up to the right
What describes a typical distribution of F-ratios?
Positively skewed with all values greater than or equal to zero
In an analysis of variance, which of the following is determined by the size of the sample mean?
SSbetween
In analysis of variances, what is measured by the MS values?
Sample Variance
What is measured by the denominator of the z-score test statistic?
The average distance between M and u that would be expected if Ho was true
What is measured by estimated standard error (SM)?
The average distance between a sample mean and the population mean.
Why are t statistics more variable than z-scores?
The extra variability is caused by variation in the sample variance.
As sample variance increases, what happens to the likelihood of rejecting the null hypothesis and what happens to measures of effect size such as r2 and Cohen's d?
The likelihood decreases and measures of effect size decrease.
In a repeated-measures analysis of variance, how does the magnitude of the mean differences from one treatment to another contribute to the F-ratio?
The mean differences add to the numerator of the F-ratio
What value is estimated with a confidence interval using the repeated-measures t statistic?
The mean for a population of difference scores
Under what circumstances should the Spearman correlation be used?
The original data are measured on an ordinal scale of measurement.
What is a serious concern with a repeated-measures study?
The results will be influenced by order effects.
If a two factor analysis of a variance produces a statistically significant interaction, what can you conclude about the main effects?
The significance of the main effects is not related to the significance of the interaction
For an independent-measures research study, what is measured by Cohen's d or r2?
The size of the difference between the two treatments.
If other factors are held constant, what happens to a confidence interval if the size of the sample increases?
The standard error decreases and the width of the interval decreases.
If a researcher is using a t statistic to test a null hypothesis about a population, what information is needed from the population to calculate the t statistic?
The t statistic does not require any information about the population.
Which of the following describes the effect of increasing sample size?
There is little or no effect on measures of effect size, but the likelihood of rejecting the null hypothesis increases
Which of the following are sources of variability that contribute to SSbetween treatments in a repeated ANOVA?
Treatment effect and random unsystematic differences.
Under what circumstances are post tests necessary?
When you reject the null hypothesis with more than 2 treatment conditions.
When is there a risk of a Type II error?
Whenever the decision is "fail to reject Ho"
A researcher measures driving distance from college and weekly cost of gas for a group of commuting college students. What kind of correlation is likely to be obtained for these two variables?
a positive correlation
The results from a study indicate that adolescents who watch more violent content on television also tend to engage in more violent behavior than their peers. The correlation between amount of TV violent content and amount of violent behavior is an example of...
a positive correlation
If a repeated-measures study shows a significant difference between two treatments with alpha level of .01, then what can you conclude about measures of effect size?
a significant effect does not necessarily mean that the effect size will be large
As the sample size gets larger, what happens to the size of the correlation that is needed for significance?
it gets smaller
In a two-factor analysis of variance, the F-ratios for factor A, factor B, and the AxB interaction:
may have different df values and may have different denominators.
In a two-factor analysis of variance, a main effect is defined as...
the mean differences among the levels of one factor (average of the differences)
Which of the following is the correct null hypothesis for an independent-measures t test?
µ1 - µ2 = 0
Which of the following is the correct null hypothesis for a repeated-measures t test?
µD = 0