Exam 1
What are the degrees of freedom for the related samples t-test?
(n-1)
What is the z-score for scores in the top and bottom 2.5%?
+/-1.96
A researcher determines that students are active about 60±12 (M±SD) minutes per day. Assuming these data are normally distributed, what is the z-score for students being active 48 minutes per day?
-1.0
A researcher determines that students study an average of 80±20 (M±SD) minutes per week. Assuming these data are normally distributed, what is the z-score for students studying 60 minutes per week?
-1.0
What is the z-score for scores in the bottom 5%?
-1.645
A researcher selects a sample of 64 participants from a population with a mean of 10 and a variance of 16. What is the standard error of the mean?
0.5
A professor finds that the students scored a 76±8 (M±SD) on the final exam. On this exam, a score of 90 is an A. Assuming these data are normally distributed, what is the z-score for 90 (the cutoff for an A)?
1.75
A researcher selects a sample of 32 participants who are assigned to participate in a study with one group. What are the degrees of freedom for this test?
31
Which of the following research studies MUST include a quasi-independent variable?
A researcher records the number of tasks completed simultaneously by men and women
Which of the following is an example of a situation in which a quasi-independent variable is used?
A variable is measured that is inherent to the participant and so random assignment can not be used
A naturalistic observation is the observation of behavior in the natural setting where:
All of the above (the behavior is expected to occur, the behavior naturally operates, there is no attempt to overtly manipulate the conditions of the environment where the observations are made)
Most behavior is believed to ________ a normal distribution.
Approximate
Suppose that a researcher selects a sample of 50 participants from a population. If the shape of the distribution in this population is positively skewed, then what is the shape of the sampling distribution of sample means?
Approximately normally distributed
A type of existing data design in which events or behaviors are described based on a review and analysis of relevant historical or archival records is called:
Archival research
A research design in which different participants are observed one time in each group of a research study is called:
Between-subjects design
A threat to internal validity in which participation in one group causes changes in performance in a second group, is called:
Carryover effects
The qualitative analysis of a single individual, group, or organization used to illustrate a phenomenon, explore new hypotheses, or compare the observations of many cases is called:
Case study
A group of individuals who share common statistical or demographic traits or characteristics is called a:
Cohort
As sample size increases, the standard error of the mean
Decreases
A measure of the size of an effect in a population is called
Effect size
The mean of the sampling distribution of sample means is
Equal to the population mean
A key difference between a t-statistic and a z-statistic is that the standard error is ________ to compute a t-statistic.
Estimated
A researcher reports a significant effect in some population. If he computes both an eta-squared and an omega-squared effect size estimate, then which estimate will be the largest?
Eta-squared
Which of the following is not one of the four steps to hypothesis testing?
Evaluate the plan
A researcher finds that the average preschool-aged child drinks two cups of milk per day. Assuming these data are normally distributed, the z-score for the average cups per day in this example is
Exactly equal to 0
A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called
Hypothesis testing
The related samples design can ________ the power to detect an effect by making the standard error ________.
Increase; smaller
A possible threat to internal validity in which the measurement of the dependent variable changes due to an error during the course of a research study, is called:
Instrumentation
Each of the following is an advantage for using the related samples design, except
It increases the variability measured in a study
Based on the effect size conventions, d = 0.99 is a
Large effect size
A researcher tests the hypothesis that weight gain among college freshman is greatest for students who are very impulsive. To test this hypothesis, he records impulsivity and weight in a sample of high school seniors, and again records these measures in the same sample after these students finished their freshman year of college. What type of developmental research design is described in this example?
Longitudinal
A researcher believes that increasing attention given to children will improve mean academic performance. Therefore, the alternative hypothesis should be:
Mean academic performance will increase
Based on the effect size conventions, d = 0.60 is a
Medium effect size
The extent to which a research setting physically resembles or looks like the natural or real-world environment being simulated, is called:
Mundane realism
One difference between a repeated measures design and a matched samples design is that
Only one design involves observing the same participants in each group
A(n) ________ is a description of some observable event in terms of the specific process or manner by which it was observed or measured)
Operational definition
A threat to internal validity in which the order that participants receive different treatments or participate in different groups causes changes in the dependent variable is called:
Order effects
A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect?
Population B
In hypothesis testing, a researcher can never
Prove that his or her hypothesis is correct
The denominator of the test statistic for a related samples t-test
Provides an estimate of the error associated with the difference scores
A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12. She determines that the mean IQ in this sample is 104. Assuming she computes a one-independent sample z-test at a .05 level of significance, what is the decision for a two-tailed test?
Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the population
A researcher placed male rodents in the presence and absence of a conspecific male. Cortisol (a stress hormone) levels were compared at both times. What type of t-test is most appropriate for this study?
Related samples t-test
A researcher compares the difference in the amount of texting by students in class during the first week and last week of classes. The type of design described here is called a
Repeated measures design
A researcher records the time it takes (in seconds) for participants to respond (by pressing a key) to a familiar versus an unfamiliar word flashed onto a computer screen. In this study, the difference in response time for each participant is compared. The type of design described here is called a
Repeated measures design
A type of related samples design in which participants are observed more than once is called a
Repeated measures design
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 18, μ = 8, σ = 2.4Researcher B: n = 12, μ = 8, σ = 2.4
Researcher A
Two researchers select a sample for a population with a mean of 12.4 and a standard deviation of 9. Researcher A selects a sample of 30 participants. Researcher B selects a sample of 40 participants. Which sample is associated with a smaller standard error?
Researcher B's, because the sample size was larger
A researcher selects two samples. In Sample 1, r = -0.77. In Sample 2, r = +0.68. In which sample is the correlation stronger?
Sample 1
Which of the following is an appropriate graphical summary of a correlation between two factors?
Scatter plot
________ is the acquisition of knowledge through observation, evaluation, interpretation, and theoretical explanation
Science
The normal distribution is symmetrical, which means that
Scores above the mean are distributed the same as scores below the mean
Suppose a researcher wants to make sure that the probability of committing a Type I error is less than 5%. How can the researcher control for this?
Set the alpha level at 0.05
The first step to hypothesis testing requires that a researcher
State the hypothesis
What is the implication for the tails of a normal distribution being asymptotic?
That extreme scores are possible in a normal distribution
The generalizability of outcomes in a research design directly relates to:
The external validity of the study
A researcher creates two groups. In one group, children played with a toy that made noise. In a second group the children played with the same toy but it did not make noise. The time spent playing with each toy was recorded) The control group in this example is:
The group in which the toy did not make noise
The power of the decision-making process is
The likelihood of rejecting the null hypothesis
A researcher randomly assigns participants to complete a crossword puzzle with or without music) The time it takes to complete the crossword puzzle is compared between groups. The experimental group in this example is:
The music group
Which of the following is an assumption for computing the related samples t-test?
The population being sampled from is normally distributed, the population variance of difference scores is unknown, samples are related or matched between groups but not within groups
To compute a related samples t-test, a researcher has to know many values. Which of the following is NOT a value that the researcher must know to compute this test?
The population variance of difference scores
Researchers state a level of significance in terms of an alpha level. The alpha level indicates
The probability of committing a type 1 error, the probability of incorrectly rejecting the null hypothesis, the probability value for rejecting the rejection region
A researcher measures the number of tasks men and women can complete in a 5-minute test. In this example, gender (men, women) is:
The quasi-independent variable
State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the right of the mean, or the area between z = ±1.00.
The second area is bigger
Each of the following is needed to compute the estimated Cohen's d, except
The standard error
The normal distribution has all of the following characteristics, except that
The total area under the curve is greater than 1.0
State whether the first area is bigger, the second area is bigger, or the two areas are equal: the area to the left of z = 0.80, or the area to the right of z = -0.80.
The two areas are the same
For the related samples t-test, assuming that all other values remain constant, then as samples size increases,
The value of the test statistic increases, the power to detect an effect increases, the estimate for standard error decreases
A researcher computes a test statistic and finds that the p value for this test is .03. What does this result mean?
There is a 3% likelihood of obtaining the test statistic value, if the null were true
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 25, μ = 5, σ = 7Researcher B: n = 25, μ = 32, σ = 7
They both have the same standard error
A researcher obtains z = 2.04 for a one-independent sample z-test. What is the decision for this test at a .05 level of significance?
To reject the null hypothesis
A professor finds that the average SAT score among all students attending his college is 1150, with a standard deviation of 150. He polls his class of 25 students and finds that the average SAT score is 1200. Suppose he computes a one-independent sample z-test at a .05 level of significance. What is his decision?
To reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test
A researcher obtains z = -.645. What is the decision for a one-tailed test, upper-tail critical, at a .05 level of significance?
To retain the null hypothesis
A researcher obtains z = 1.45 for a one-independent sample z-test. What is the decision for this test at a .05 level of significance?
To retain the null hypothesis
A researcher directly controls for the probability of a ________, but does not directly control for the probability of a ________.
Type 1 error; type 2 error
The sample variance is an unbiased estimator of the population variance
When dividing SS by df; when dividing SS by n-1
The probability of committing a Type I error is stated by ________; the probability for committing a Type II error is stated by ________.
alpha; beta
A professor computes the mean difference in exam scores before and after a lecture as 9.0±14.5 (Mean Difference ± Standard Error of the Difference), and this difference was significant. What is the effect size for this result using estimated Cohen's d?
d=0.62, medium effect
A professor compares scores on a competency exam among students at two times during a single semester. What type of t-test is most appropriate for this study?
related samples t-test
The ________ is an inferential statistic used to determine the number of standard deviations in a t-distribution that a sample mean deviates from the mean value or mean difference stated in the null hypothesis.
t-statistic
A researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule. Assuming that the population variance in unknown, what type of t-test is appropriate for this study?
two independent sample t test
