Stats exam 3
The value of Pearson's r ranges between ______.
-1.0 and +1.0
You find a correlation between creativity and academic honesty of r = .40. The coefficient of determination for this relationship is ______.
.16
According to the null hypothesis for a simple experiment, we expect the difference between the means of our two groups to be ______.
0
If we find a perfect correlation, the standard error of the estimate would equal ______.
0
The expected value of F if the null hypothesis is true is ______.
1
The results above suggest there is a probability of ______.
1.3% for a Type I error
Ben is researching the effect of sleep deprivation on test scores. He finds a significant effect and computes the effect size of rpb2 = .15. This can be interpreted as meaning ______.
15% of the variability in test scores is accounted for by sleep deprivation
There are ______ regression equations for two correlated variables.
2
Shawn examines the relationship between creativity and academic honesty and finds the coefficient of determination equals .33 or r2 = - .33. This means that ______.
33% of the variability in academic honesty is accounted for by knowing its relationship with creativity
A 95% confidence interval of 2.68 < µ1 µ2 < 5.79 tells us that we can be ______.
95% confident that the mean difference from the study represents a population of mean differences falling between 2.68 and 5.79
______ is when participants withdraw from a study.
Attrition
The one-way ANOVA compares ______.
Correct between-groups variance and within-groups variance
Which of the following statements is correct?
Correlation is a prerequisite for causation.
The post hoc test above shows that ______.
Group 2 significantly differs from Groups 1 and 3 which do not differ
A researcher wants to examine the effect of violent computer games on verbal aggression. She has college students play 45 min, 30 min, 15 min, or no minutes of a violent computer games. Which of the following best represents a nondirectional alternative hypothesis for this study?
Ha: There will be a difference in verbal aggression after playing 45 min, 30 min, 15 min of no minutes of a violent computer game.
You believe that students anxiety is related to test scores in Research Methods. The alternative hypothesis stated in numerical terms would appear as ______.
Ha: r ≠ 0
A researcher conducts a one-group pretest posttest design. The researcher administers the pretest but has a colleague administer the posttest. ______ is a threat to the study's internal validity.
Instrumentation
The formula for the independent-samples t test is ______.
M1 - M2/SDX - X
The statistic used to determine whether a linear relationship exists between two interval/ratio variables is the ______.
Pearson's r
You believe that students anxiety is related to test scores in Research Methods. Which of the following represents a directional alternative hypothesis for your study?
Students anxiety will be negatively related to their test scores in Research Methods.
The regression equation is always represented by the formula ______
Y' = bX + a
In the regression equation, a = ______.
Y-intercept
The Hawthorne effect is ______.
a phenomenon in which participants change their behavior simply because they are in a study and have the attention of researchers
The scatterplot for a perfect correlation would show ______.
a straight line
One reason that correlational designs do not establish causality is ______.
a third variable could be responsible for the relationship between our variables
The assumptions for the independent samples t test include ______.
an IV that is dichotomous, DV that is interval or ratio, independent groups, homogeneity of variance
A researcher conducts a study in which he randomly assigns participants to either read a scenario about a man or about a woman. As a manipulation check, he might ______.
ask participants to report the gender of the person described in the scenario
he mean square within groups represents the ______.
average deviation within all groups of the study
The standard error of the difference between means (SDX - X) represents the ______.
average variability in a sampling distribution of differences between means
Correlational designs can have greater external validity than experiments because correlational designs ______.
better represent the everyday world where we do not manipulate or control events
After a study, which assessed the anxiety of students before a Research Methods test, the researcher reports that all the students scored between 20 and 25 on the 25-point scale of anxiety. What problem might exist with the scale?
ceiling effect
An educational researcher randomly assigns 20 health classes to either receive a violence prevention curriculum for 5 weeks or to receive the usual health curriculum during the five weeks. What type of random assignment is this?
cluster random assignment
The statistic that describes the proportion of variability that is accounted for by knowing the relationship between two variables is the ______.
coefficient of determination
The pooled variance is the ______.
combined and weighted variances of the two groups in a simple experiment
Someone who is working with the researcher but pretends to be a participant or bystander is called a ______.
confederate
A variable that varies systematically with the variables of interest in a study and is a potential alternative explanation for causality is called a(n) ______.
confound
the point-biserial correlation coefficient (rpb) is used to analyze the ______
correlation between a dichotomous and an interval/ratio variable
The three major types of designs with two independent groups are ______.
correlational, quasi-experiments, simple experiments
Jesse is studying the effect of daily exercise on happiness. His directional alternative hypothesis might state ______.
daily exercise will increase happiness
What is one advantage of conducting a multiple independent-groups design over multiple simple experiments?
decreasing the probability of Type I error and confounds
A blind-experiment helps reduce ______.
demand characteristics
A double-blind experiment helps reduce ______.
demand characteristics and experimenter expectancy effects
A researcher conducts an experiment to examine the effect of exercise on memory. Memory is the ______.
dependent variable
Degrees of freedom in for an independent-samples t test is computed by ______.
df = (n1 - 1) + (n2 - 1)
We select the critical value of r from the table of values based on the ______.
df, criterion level, and type of alternative hypothesis (one- or two-tailed)
______ validity is a type of external validity that assesses the degree to which a study's findings generalize to real-world settings.
ecological
One reason to prescreen participants is to ______
ensure that the study is ethical
A researcher conducts an experiment in which he randomly assigns one group to complete mood questionnaires in a red room and another group to complete the questionnaires in a blue room. What type of manipulation is this?
environmental manipulation
The effect size for an ANOVA is computed using ______.
eta2
You should compute a linear regression equation when you ______.
find a significant correlation for two interval/ratio variables
We want our computed r value to be ______ the critical value listed in the table in order for it to be significant.
greater than
Assumption for a one-way independent samples ANOVA include ______.
groups are independent
If you are conducting a study and the lights go out, which of the following threats to internal validity now limits your study?
history
The assumption that variances in populations are the same is called ______.
homogeneity of variance
The strength of the relationship is evident from ______ and the direction of the relationship is evident from ______ in a correlation coefficient.
how close the correlation coefficient is to the absolute value of 1.0; the sign of the coefficient
Anne and Jack are examining variables related to self-control. Anne finds r = +.40 between percentage of salary saved and self-control while Jack finds r = .60 between impulsivity and self-control. Which variable is more strongly related to self-control?
impulsivity
A researcher conducts an experiment to examine the effect of exercise on memory. Exercise is the ______.
independent variable
A(n) ______ is manipulated in an experiment.
independent variable
The inferential statistic used to analyze two-group designs is called the ______.
independent-samples t test
A researcher conducts an experiment in which she randomly assigns one group to listen to directions and another group to read directions. What type of manipulation is this?
instructional manipulation
Which of the following variables could serve as an IV in an experiment?
instructions to participants
Which of the following is one of the threats to internal validity due to experiences or environmental factors?
instrumentation
The extent to which we can say that one variable caused a change in another variable is called ______.
internal validity
A confidence interval defines the ______.
interval that includes the population mean difference represented by the mean difference in our study
A correlational design ______.
is a type of study that tests the hypothesis that variables are related
A researcher conducts a group design to determine the effect of Variable A on Variable B. The researcher can eliminate or control for the threats of history, maturation, testing, and instrumentation by ______.
keeping everything, except Variable A, constant across groups
Kyle is conducting an experiment on the effect of monitoring on unethical behavior during tests. One group has an identified TA monitoring the test while the other group has no obvious monitor in the room. As the students turn in their test, they are asked if there was a monitor in the room during the test. This is an example of a ______.
manipulation check
The process of verifying that the participants attended to the manipulation is called a(n) ______.
manipulation check
Natural changes that occur over time can be a threat to internal validity. This threat is called ______.
maturation
Researchers try to ______ between-groups variance and ______ within-groups variance.
maximize; minimize
A regression equation allows you to ______
more closely estimate the value of Y for a given X value
Della wants to predict self-control scores using education level, impulsivity, and organizational skills as self-reported by students. She should compute ______.
multiple regression
After computing a correlation, we compare our computed r value to the critical values for Pearson's r using ______ degrees of freedom
n - 2
When two variables move in opposite directions (one increases while the other decreases), they are ______.
negatively correlated
A researcher conducts an experiment examining the effect of a medication on anxiety. A control group would receive ______.
no medication
In a simple experiment, the IV is on a ______ scale of measurement and the DV is on a ______ scale.
nominal; interval or ratio
A multiple independent-groups design examines the effect of ______.
one IV with three or more levels on a DV
A researcher hypothesizes that A causes B. He gives all participants a pretest to assess Variable B, then exposes them to Variable A and then gives them a posttest to assess Variable B. What type of design is this?
one-group pretest posttest
The inferential statistic used to analyze a multiple independent-groups study is ______.
one-way ANOVA
The scatterplot above shows a ______.
perfect positive relationship
You want to examine the relationship between owning a house (yes - no) and income. You would compute a ______.
point-biserial correlation coefficient
The effect size for an independent-samples t test can be assessed using a(n) ______.
point-biserial correlation squared
When two variables move in the same direction together (both increase or both decrease), they will be ______.
positively correlated
Correlational designs include a ______ instead of an IV and a ______ instead of a DV.
predictor; outcome
The process of identifying those who have characteristics that the researcher wants to include or exclude in the study is called ______.
prescreening
A(n)______ is a group design in which a researcher compares preexisting or naturally occurring groups that are exposed to different levels of a variable of interest.
quasi-experiment
The interpretation of the results for quasi-experimental designs differs from that of an experiment because ______.
quasi-experiments examine relationships while experiments examine causation.
If a researcher conducts a dependent-groups experiment in which the participants experience all levels of the independent variable (IV), what type of random assignment should he use?
random assignment to order of conditions
If tobt = 1.98 and tcrit = 2.16, we would ______.
retain the null hypothesis
The presence of a confounding variable means that you have not ruled out which of the following criteria for causality?
ruling out alternative explanations
A researcher conducts a study examining the effect of exercise on mood. She recruits participants from a health club to exercise for 30 min and then report their mood. She then recruits participants from a book club to sit for 30 min and then report their mood. Because the groups were different prior to the study, ______ is a threat to the study's internal validity
selection
the treatment administered to one group is shared with another group through cross-group interactions
sensitivity to change
If you hypothesize that Variable A will cause a change in Variable B, you must design a study so that Variable A comes before Variable B. This is to test that the relationship meets the criteria of ______.
sequencing
A study that manipulates a variable under two conditions, randomly assigns participants to one of those two conditions, and measures its effect on another variable while controlling all other conditions is called a ______.
simple experiment
A researcher designs an experiment with two groups. She decides to randomly assign participants to group by having each participant pull a number (1 or 2) out of a hat. What type of random assignment is this?
simple random assignment
in the regression equation, b = ______
slope
To determine where our mean difference falls on the sampling distribution that predicts no difference we need to know the standard deviation of the sampling distribution. This term is called ______.
standard error of the difference between means
The average error between predicted Y values and the actual Y values is called ______.
standard error of the estimate
Extreme scores tend to move closer to the mean over time. This is due to ______.
statistical regression
Which of the following is one of the threats to internal validity due to participant characteristics?
statistical regression
A one-group pretest posttest design is subject to which of the following threats to internal validity?
statistical regression, history, maturation, testing, and instrumentation
A researcher designs an experiment with two groups. She decides to randomly assign participants by first dividing participants based on gender. She then randomly assigns the males by having them pull a number out of a hat, and then does the same for the females. What type of random assignment is this?
stratified random assignment
A correlation coefficient provides two pieces of information about a relationship. They are the ______.
strength and direction of a relationship
In a study of the effect of daily exercise on happiness suppose we found that happiness (rated on a 25-point scale) was significantly higher (p = .03) for a group that exercised daily (M = 21.50) than for a group that exercised once a week (M = 15.50). We could interpret the practical significance of this study as ______.
strong because the average happiness ratings are very different and we could assume that the participants would notice the different levels of happiness that the ratings represent
The scatterplot above shows a ______.
strong positive relationship
The results of an ANOVA are typically presented as above in a ______, which in this case shows ______.
summary table; no difference between four groups on cognitive awareness
Giving a pretest might result in which of the following threats to internal validity?
testing
When entering data to analyze a correlation, you should be careful to enter ______.
the data in pairs for each participant, with the X value in one column and the Y value in the next column on the same row
Random assignment is used in an experiment so that ______.
the groups are as similar as possible prior to the IV manipulation
The sampling distribution for an independent-samples t test is a distribution of the differences between _____.
the means of the two groups in our study
The line of best fit represents ______.
the predicted Y values (Y') for each X value in the sample range
Diffusion of treatment occurs when ______.
the treatment administered to one group is shared with another group through cross-group interactions
Correlation is the statistic used to assess ______.
the validity and reliability of measures
We should not compute a regression equation if we do not find a significant correlation between two variables because ______.
there will be too much error in our predicted values
Confounds that must be controlled so that a cause effect relationship can be demonstrated are called ______.
threats to internal validity
The formula for F is ______.
treatment variance + error variance/error variance
In a simple experiment examining the impact of violent games on aggressive thoughts, we might have participants play a violent game for 45 min rather than 5 min. This decision reflects our attempt to maximize power by ______.
using a strong manipulation of our IV
We can increase the power of a correlational study by ______.
using measures that are valid and reliable
Steps we can take to ensure that our DV is reliable and valid include ______.
using more than one item to measure our DV
Levene's test tells us if ______.
we have violated our assumption of homogeneity of variance
The ______ the correlation, the ______ the standard error of the estimate.
weaker; larger
One reason to use a correlational design is ______.
when an experimental study would be unethical