Effect sizes are calculated ______ the study
after
A study reports finding a "significant" difference between group means. what should we conclude about this report?
ch 8
In Cohens'd, the father apart the means of two distributions, the ___ the effect size, assuming the standard deviation is held constant.
Higher
The _____ estimates acknowledges the amount of uncertainty in the ______ estimate by reporting the margin of error.
Interval; point
Of the following, which is not a benefit of performing a meta-analysis?
It increases the chances of misinterpreting data by analyzing half of the studies
The critical cutoffs for a 95% confidence interval are -1.96 and 1.96. What are the cutoffs for a 90% confidence interval?
-1.65 and 1.65
Glen has limited funds left in his grant to pay participants to be in his experiment. He wants to know how many participants he needs to detect a deference between conditions. What statistical technique would help him estimate how many participants he nee
power analysis
If you ran the same study 20 times, you would expect to find a mean in (or at) the _____ 95% of the time, with a p value of 0.05
confidence interval
We can enhance power by decreasing the standard deviation in our sample. This can be accomplished by all of the following except:
working with biased sample.
When comparing the difference between means for two distributions, what happens to the effect size if the variability with each distribution becomes smaller?
The effect size increases
A Cohen's d value of 0.2 indicates how much overlap between distributions?
85%
While the population information about SAT scores includes a mean of 500 with a standard deviation of 100, a researcher finds a sample of 32 honors students with an average SAT score of 580. The test statistic is ____________, and the Cohen's d measure of
4.53; 0.80
Increased sample size serves to enhance power because
variability within the distribution is reduced and standard error is smaller.
Power can be thought of as the percentage of the distribution of means, centered around your sample mean, that falls:
within the critical cutoff regions, where the null hypothesis can be rejected.
The practical use of statistical power is that it informs you the researcher:
how many participants are needed to conduct a study that will produce quality data that you can trust
Imagine that the confidence interval around a group's mean is [-0.27, 0.33], what is the mean?
0.03
Imagine that the confidence interval around a test average is [70%, 90%]; what is the point estimate?
80%
Which of the following accurately captures the difference between a confidence interval and confidence level?
The confidence interval is the range of scores around the mean about which we have a level of confidence.
Michelle is a cognitive psychologist studying reading times for stories that contain either consistent or inconsistent information. She runs 38 people through her study and concludes that reading times slow when coherence breaks occur in a story. Specific
point estimate
A researcher collects 15 data points that yield a mean of 9.164 and a standard deviation (based on N - 1) of 2.377. What is the standard error for the distribution of means?
0.614
According to the Consumer Action group, the average credit card interest rate in 2010 was 12.83% (based on a sample of 39 cards). A researcher wanted to know if college students at her institution have different interest rates compared to this national st
College students have different interest rates on average compared to the nation.
After performing a paired-samples t test as part of a hypothesis test, it is recommended by the APA that researchers also consider:
calculating a confidence interval and a measure of effect size.
For the paired-samples t test, the comparison distribution:
contains means of difference scores.
A researcher collects 15 data points that yield a mean of 9.164 and a standard deviation (based on N - 1) of 2.377. If he is comparing the sample to a population mean of 10.6, what is the value of the test statistic
-2.339
A single-sample t test is conducted on a sample of 26 people who were selected from a large population estimated at 2500 people. The critical cutoff for a two-tailed test at a p level of 0.05 would be:
-2.060 and 2.060.
At a sample size of infinity, the t distribution:
is identical to the z distribution.
Degrees of freedom" refers to what on a t table for a single-sample t test?
number of scores that are free to vary in estimating population parameters, N -
The critical cutoffs for a two-tailed, paired-samples t test with N = 9, at a p level of 0.01 are:
-3.356 and 3.356.
Griffin is looking through a statistics text for a z table, but he can find only a t table in the index. What tip would best help him find the information he needs?
Use the sample size of infinity listed in the t table because it is equal to the z table.
The correct formula for Cohen's d for a paired-samples t test is:
(M - \mu)/s
The major difference between the paired-samples t test and the single-sample t test is that in the paired-samples t test:
we must create difference scores for every individual.
Psychology students took longer to complete a quiz when music was playing in the background than when there was no background noise: t(19) = -4.01, p < 0.05. What is the sample size in this study?
N=20
Which of the following equations is the correct formula for the t statistic for a distribution of means?
(M- Um) / Sm
Using the data 1, 2, 3, 4, and 5, compute the standard deviation first without the correction and then with the correction used when estimating a population
1.41; 1.58
When scientists call a hypothesis test conservative, they mean that it is:
difficult to reject the null hypothesis (i.e., the status quo).
The t statistic is more ________ than the z statistic because we are less likely to observe an extreme t statistic.
conservative
An independent-samples t test was conducted to compare high-altitude exercise to exercise at sea-level. Imagine the mean comfort level of participants, rated on a 7-point scale where high values reflect high comfort, at high altitude was 3.5 while the ave
-2.030 and 2.030
An independent-samples t test was conducted to compare gas expenses of diesel truck owners to owners of regular gas trucks. Imagine the mean gas consumption in one week amounted to $68 for diesel trucks and $84 for regular gas trucks. Imagine also that va
-2.32
An independent-samples t test is a ________ design.
between-groups
An independent-samples t test was conducted to compare high-altitude exercise to exercise at sea-level. Imagine the mean comfort level of participants, rated on a 7-point scale where high values reflect high comfort, at high altitude was 3.5 while the ave
fail to reject the null hypothesis, the test statistic did not exceed the critical cutoff
An independent-samples t test was conducted to compare high-altitude exercise to exercise at sea-level. Imagine the mean comfort level of participants, rated on a 7-point scale where high values reflect high comfort, at high altitude was 3.5 while the ave
-1.12
An independent-samples t test was conducted to compare gas expenses of diesel truck owners to owners of regular gas trucks. Imagine the mean gas consumption in one week amounted to $68 for diesel trucks and $84 for regular gas trucks. Imagine also that va
-2.27
If you want to use three groups (a control group and two experimental groups) to compare differences on an IQ test, would an independent-samples t test be appropriate? Explain.
No; there are more than two groups.
By weighting the two estimates of variance in our calculation of pooled variance, we are able to allow the estimate based on a larger sample to contribute more to the calculation. We do this because:
it is the more trusted estimate of variance, as large samples tend to provide greater accuracy.
A researcher conducts an independent-samples t test comparing two group means of 11.3 and 12.7. She also obtains values of 2.2 for sdifference, 4.64 for pooled variance, and 40 for degrees of freedom total. What is the value of the test statistic?
-0.64
If you want to use a control group as well as the experimental group, which type of t test is most appropriate and why?
independent-samples t test; it is a two-sample, between-groups design
The results of an independent-samples t tests are compared to a distribution of:
differences between means based on samples of the same size as those studied.
In calculating pooled variance, why do we make adjustments for sample size?
Estimates of spread from smaller sample sizes are likely to be less accurate than estimates of spread from larger sample sizes.
The results, t(22) = 1.08, p > 0.05, indicate that the ________ is plausible based on this limited sample.
null hypothesis
In an independent-samples t test, each group has N minus________ degree(s) of freedom.
1
Which of the following equations is the correct formula for calculating degrees of freedom for an independent-samples t test?
dftotal = dfx + dfy
Which of the following is not one of the assumptions of the independent-samples t test?
Large samples should contribute more to weighted averages than small samples.
When computing the confidence interval for an independent-samples t test, we find the critical cutoffs using the:
total degrees of freedom
Unnithan, Houser, and Fernhall (2006) were interested in whether playing the game Dance Dance Revolution (DDR) affected the heart rate of overweight and nonoverweight adolescents differently. A group of 22 adolescents, 10 classified as overweight and 12 a
Independent sample - t test
A researcher examines the effectiveness of different body lotions by having 12 participants apply four different lotions to the same, unique body locations daily for two weeks. For example, lotion #1 is always applied to the right thigh, while lotion #2 i
random selection
A researcher conducts a within-groups ANOVA, fails to find a significant F statistic for the independent variable, and finds an R2 value of 0.02. What does the effect size statistic tell us about the research?
The conventions for R^2 indicate that this is a small effect, which would help to explain the non-significant F statistic.
After completing a significant ANOVA, you should perform ________ to determine where significant between-group differences exist. For ANOVA, we use _______.
post hoc test; Tukey HSD
A researcher compares bone density in retired professional athletes across three different sports. He computes a series of three t tests to examine all between-group differences, running each test with a p level of 0.01. What is the probability of a Type
0.03 or a 3% chance
In the three statistics F, z, and t, we divide ________ variability by ________ variability to analyze the relation between variables
between-groups; within-groups
Following a one-way within-groups analysis of variance that results in a significant F statistic, the researcher should:
conduct post-hoc tests, such as Tukey HSD, to determine where the significant differences between levels of the independent variable exist.
Congratulations; you found a significant result using a one-way ANOVA to compare the mean of four age groups (3 years old, 5 years old, 8 years old, and 12 years old) on a test of language ability. What specific conclusions can you draw from this result?
Language ability of 3-, 5-, 8-, and 12-year-olds was not the same.
Does the F distribution take into account individual differences when comparing sample means?
Yes; as the variability within the individual samples decreases, the F statistic becomes larger since the distributions are not overlapping very much.
A Tukey HSD is computed to compare two groups following an ANOVA that compared five groups. The within-groups degrees of freedom for the test are 7, and the computed HSD value is 6.24. What would you conclude about this analysis if evaluated at a p level
The test statistic is significant, revealing a statistical difference between the two groups.
The multiple-group equivalent of a paired-samples t test is the:
one-way within-groups ANOVA.
Rousseau visually inspects her data before analyzing it only to find that the populations that she sampled appear to have very different variances although her sample sizes are equal. Which assumption of ANOVA has she violated and what should she do?
Homoscedasticity; she should proceed as long as the largest variance is not greater than two times the smallest variance and report it with her statistics.
When researchers use ANOVAs to report results of case studies that include only one participant, they typically violate the assumption of random selection. How does this action affect the conclusions of the study?
The external validity is low, and they cannot generalize their results beyond the sample.
The one-way within-groups ANOVA is used when we have:
one nominal or ordinal independent variable with more than two levels, a scale dependent variable, and every participant is in every group.
The subjects sum of squares calculated in the one-way within-groups ANOVA assesses:
the variability due to participant differences.
Which of the following statistical analyses can handle multiple measures or repeated-measures based on the same individuals?
one-way within-groups ANOVA
Which of the following is NOT an assumption of an ANOVA?
The samples should be from a population with a known mean and standard deviation.
Which of the following is a potential problem with a within-groups design for ANOVA?
The order that conditions is presented could impact the dependent variable.
You have found a statistically significant difference between means using an ANOVA that you had not previously predicted. To identify where the differences between means lie, which test should you run?
Turkey HSD
When we reject the null hypothesis after using an F table to determine the significance value, we can conclude that there is:
a difference between means that is larger than we would predict by chance.
A researcher investigates the impact of color and lighting on mood at work. He manipulates the paint used in offices, including the presentation of four different colors. He also manipulates lighting by using three different lighting conditions. The null
the effect of office color is not dependent on the type of lighting condition.
A bar graph displays the mean scores on a test of mental rotation for students majoring in psychology or chemistry who have either high or low spatial abilities. Psychology and chemistry students with low spatial skills scored about 35% correct on the men
There appears to be a main effect of spatial ability only.
In a ________, the strength of the effect but not the ________ varies under certain conditions.
quantitative interaction; direction
A student researcher conducts a study that is analyzed using a two-way between-groups ANOVA. Unfortunately, none of the three F statistics were statistically significant. The student is confident that there is something to his research question, and he wo
the second main effect because it has a medium effect size
The Educational Testing Services (ETS) is conducting a study to determine the relation between method of presentation (standard lecture vs. computer presentation) and type of lecture (psychology, English, statistics) to lecture comprehension. What kind of
Two-way ANOVA: Factor 1 is presentation, with two levels (standard vs. computer), and factor 2 is lecture type, with three levels (psychology, English, and statistics).
Suppose you are examining the relation between patrol location (more affluent vs. less affluent neighborhoods) and amount of training (5 weeks, 10 weeks, or 15 weeks) to police job performance in a small town. You find a significant interaction in that th
quantitative interaction.
Overall, children did not remember more words than did adults on a memory test, F (1, 153) = 3.00, p > 0.10, and participants listening to music during the test did not remember more words than those not listening to music, F (1, 153) = 1.98, p > 0.10. Ho
interaction of age and music
What does a two-way ANOVA offer beyond what two separate one-way ANOVAs can tell us about our data?
a chance to see how the effect of one variable can depend on the levels of another variable
Which statement best describes an interaction in a two-way ANOVA?
The two independent variables have a combined effect on the dependent variable that is not present with either independent variable alone.
When determining the critical value or cutoffs for the three effects tested in a two-way between-groups ANOVA, what value always stays the same?
within-groups degrees of freedom
Which of the following is not one of the assumptions of a two-way between-groups ANOVA?
The participants are matched on important characteristics.
A marginal mean in a two-way ANOVA is the mean of the dependent variable:
at one level of. an independent variable, disregarding the distinction of levels of the other independent variable.
What is the primary limitation of the correlation coefficient?
It cannot be used to establish causal relations between two variables.
In the process of calculating a correlation coefficient, we examine deviation scores for all scores compared to their means. For a negative correlation, what is true of these deviation scores?
A negative deviation will tend to occur with a positive deviation for the other variable.
In the formula for the Pearson correlation coefficient, the calculation of variability (SS) can be found in:
the denominator.
Tysha notices that every time she wears jewelry to work she has a very productive day and finishes all her projects on time. When she doesn't wear jewelry she struggles to get everything done by the end of the day. She concludes that wearing jewelry is th
No; she cannot make causal claims from correlations.
Based on research with her patients, Dr. Sabine knows that the correlation coefficient between scores on an anxiety scale and comfort at a social gathering is -0.35. According to guidelines established by Cohen, how could we characterize the strength of t
medium
Every day for the last month, Boris has recorded the number of times it has rained and the height of all of his tomato plants. He wants to see if the two are correlated, so he creates a scatterplot of the data. He sees a pattern that he could probably dra
Yes, there appears to be a linear relationship; he should use the Pearson correlation coefficient.
_______ is a branch of statistics focused on developing accurate and unbiased tests and measurements.
psychometrics
What is the best way to test a measure's reliability over time?
test- retest
Why would you use a correlational study if you cannot make causal claims?
You cannot always manipulate variables (such as gender), and correlations allow us to examine the relationship between variables.
Which of the following expressions would represent the research hypothesis when testing for significance using the Pearson correlation coefficient?
p =/= 0
A psychometrician uses correlation to examine what important aspects of the development of measures?
reliability and validity
There is a correlation between global warming and the decline of polar bears. The most likely explanation is that:
there is a third variable causing both effects.
The incidence of depression among college students is negatively correlated with the number of sunny days each year in the locale where they attend college." This statement means that:
the chances of a college student being depressed tend to be higher with fewer sunny days.
A computer analysis that essentially calculates the average of every possible split-half correlation as a measure of reliability is known as:
coefficient alpha.
Assume that the relation between SAT scores and first-year grade point average (GPA) is stronger than between SAT and second-year GPA. If we constructed two scatterplots to represent these data, how would they compare?
The cluster of points for SAT and first-year GPA would more closely approximate a straight line.
A researcher collected data from 74 people about the number of fast-food meals eaten per week and length of commute to work in miles. Imagine the correlation was positive at 0.32. Two participants in the sample reported eating every meal out each week, to
The correlation could get stronger, increasing to greater than 0.32.
Researchers who study the process of reading in children have discovered that better readers make smoother eye movements across the page. If we drew a scatterplot of the data, the points on the graph would likely run from ________ to ________.
lower left; upper right
Which of the following values of the correlation coefficient indicates the weakest relationship between two variables?
0.03
What is the correlation between a person's weight as measured in grams and a person's weight as measured in pounds?
+1.00
explanations when we consider two variables,When we observe a correlation between two variables, there are three possible explanations. Which of the following is NOT one of those explanations when we consider two variables, variable A and variable B?
They are simultaneously causing each other.
A man and woman who are both tall, with him at 6 feet tall and her at 5 feet, 10 inches, have four children, which child represents regression to the mean for height?
Laura who is 5 feet, 5 inches tall
A multiple regression analysis revealed the following equation relating the time (in hours) it takes to complete a puzzle based on the number and size of pieces,
? = 1.5 + 0.014 (Xnumber of pieces) - 1.2 (Ysize of pieces). If a puzzle has 500 pieces, with
7.9 hours
Dr. Kim thinks his regression equation is very accurate, but he wonders if perhaps the mean is just as good at predicting scores as the regression equation. He knows that the correlation coefficient (r) for the two variables is quite high, -0.82. Should D
regression equation; the proportionate reduction in error (r2) is high
In the equation ? = 130 + 5(X1) + 3(X2), which of the following statements is true?
There are two slopes.
A researcher wants to be able to predict first-semester grade point average with as much accuracy as possible, so she would like to use both high school grade point average and SAT score as predictor variables. Which of the following techniques would be m
multiple regression
Dr. Garoule is trying to determine which of his patients has the highest likelihood of depression. He calculates a linear regression equation with the scores on an anxiety measure, which are positively correlated with scores on a scale measuring depressio
below the mean; the z score is negative
If the points on a scatterplot are all close to the regression line:
the standard error of the estimate is small.
Bing Travel attempts to predict the price of airline tickets based on travel route, dates, and purchase dates. The statistical procedure being used is known as:
multiple regression
For exploratory analysis, when we aren't sure about the nature of a relationship, a ________ is a great way to consider your data.
scatterplot
If two independent variables make lots of overlapping contributions to the prediction of the dependent variable, then:
the variables are non-orthogonal.
________ refers to the accuracy of a prediction based on the regression equation or the amount of error that is eliminated compared to predictions based on the mean of the dependent variable.
Proportion reduction in error
Predicting an individual's IQ score from two variables, for example, socioeconomic status and education level, would involve the use of:
multiple regression.
If we know a person's score on a(n) ________ variable, we can predict the person's score on the ________ variable using simple linear regression.
independent; dependent
Penny is figuring the regression line for some data but needs help in first figuring the predicted value of Y. She knows that the slope is 3 and the intercept is 4. What is the predicted Y value for an X score of 7?
25
In the equation for a line in statistics, the ________ is the predicted amount of increase for Y when X is increased by 1, and the ________ is the predicted value for Y when X crosses the y axis (X = 0).
slope, intercept
When drawing a line of best fit, it is "best" to use ________ point(s) of ________ values.
at least 2; low and high
There is an extremely high negative correlation between altitude and the percentage of oxygen in the air. Is it correct to say that high altitudes cause low amounts of oxygen in the air based on a linear regression equation and the Pearson correlation coe
No, because regression analysis does not imply causation.
The standardized regression coefficient, which is equal to the Pearson correlation coefficient in a simply linear regression, is also called:
beta weight
We can predict body weight based on the amount of calories consumed by an individual due to the positive correlation between the two variables. When looking at the line of best fit for the linear regression we can see the data points are clustered close t
calories consumed and body weight, because the variance is lower
What is the key difference between simple linear regression and multiple regression?
Simple linear regression uses one independent variable, whereas multiple regression allows for the inclusion of two or more independent variables.
What can you conclude from the following chi-square test for independence result, C2(1, N = 102) = 0.17, p > 0.05?
There is no evidence of dependency between the two variables.
Does attractiveness to people of different races or ethnic backgrounds depend on your own race or ethnicity? Mackenzie decides to collect data on this topic for a class project. She focuses on three different racial/ethnic groups for both the person and t
chi-square test for independence
Although nonparametric tests such as chi-square can be used with populations that are not normally distributed, there is still an important assumption that the data are ________.
independently sampled from the population
A Pearson correlation coefficient of 0.72 indicates a strong positive correlation, and a Spearman correlation coefficient of 0.72 indicates ________.
a strong positive correlation
A researcher wondered if belief in an afterlife differed by gender. State the null hypothesis and the research hypotheses.
Null hypothesis: belief in an afterlife is independent of gender; Research hypothesis: Belief in an afterlife depends on whether you are female or male.
One limitation of nonparametric tests is that confidence interval and effect size measures are typically not available. What is true of chi-square tests?
There is a measure of effect size, Cramer's V.
In a 2006 study, Gortmake and colleagues surveyed 80 lesbian and gay students at a large Midwestern state university to assess their experiences and their perceptions of the campus climate regarding lesbians and gays. One of the questions the researchers
3
Is there a relationship between rugby players' ability to score a goal and their height? The International Rugby Board is investigating whether there are any differences in the average rankings for number of goals scored by tall and short players in a sea
Tall rugby players and short rugby players differ in average scores per season.
In a 2006 study, Gortmake and colleagues surveyed 80 lesbian and gay students at a large Midwestern state university to assess their experiences and their perceptions of the campus climate regarding lesbians and gays. One of the questions the researchers
7.815
For a study, a chi-square statistic of 1.82 was calculated. There were 45 participants in total, and 2 degrees of freedom for the first variable and 3 degrees of freedom for the second variable. What is the effect size?
0.142
The same formula is used to calculate the chi-square statistic in the chi-square test for goodness-of-fit and the chi-square test of independence. Which calculation differs along the way for these two tests?
expected frequencies
Shay discovers his data are not normally distributed and appear to be skewed. He knows his sample size is small, but he cannot collect more data due to limited funds and time constraints. What should he do?
use a nonparametric test
________ tests are useful for comparisons of data where the dependent variable is ________.
Nonparametric; nominal
The Mann-Whitney U test is the nonparametric test used when assumptions for the ________ are violated, because it is the parallel to this parametric statistic.
independent-samples t test
The Mann-Whitney U test would be used in which of the following examples?
Ranked job satisfaction was compared for males and females at a local business.
You are transforming finishing times from a 5K race into ordinal data and you have the following scores in minutes: 17.6, 25.3, 18.4, 28.2, 32.6, and 25.3. If you rank from fastest to slowest, what would be the rank of the two people with a finish time of
3.5
Which of the following Spearman correlation coefficients is the strongest?
-0.61
When using ordinal data, we employ a nonparametric test instead of a parametric statistic because:
ordinal variables are based on rankings and will not be normally distributed.
What effect size is appropriate for a chi-square test?
Cramer's V
You are planning to perform a Pearson's correlation on interval data, but you notice several extreme outliers that appear to skew the distribution. What is the best alternative method to analyze your data?
ransform the data into ordinal rankings and perform a Spearman correlation.