Stats 221
A researcher chooses to collect data from a large sample that represents a population instead of a smaller sample. Which of the following is not a likely consequence of choosing to collect data from a large sample relative to a smaller sample?
The expected value of M will decrease.
Why are t statistics more variable than z-scores?
The extra variability is caused by variations in the sample variance.
Two samples from the same population both have M = 84 and s 2 = 20, but one sample has n = 10 and the other has n = 20 scores. Both samples are used to evaluate a hypothesis stating that µ = 80 and to compute Cohen's d. How will the outcomes for the two samples compare?
The larger sample is more likely to reject the null hypothesis, but the two samples will have the same value for Cohen's d.
An educational specialist develops a new teaching technique for a nutrition course. The educational specialist knows that typically scores on a well-validated measure of nutrition knowledge are normally distributed with µ = 20 and σ = 8. The educational specialist administers their new teaching technique to a sample of n = 25 students who subsequently score M = 22.5 on the measure of nutrition knowledge. Which conclusion can the educational specialist make based on the results of this research study?
The new teaching technique does not have an effect on nutrition knowledge because the computed z-score does not reach the z = ±1.96 threshold.
The results of a hypothesis test are reported as follows in a scientific report: t(17) = +2.76, p < .05. Based on this information, which statement below is not correct?
The probability that there is a statistically significant effect is less than 5%.
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 researcher does not need to know any information about the population.
A sample of n = 25 individuals is selected from a population with µ = 80, and a treatment is administered to the sample. Which outcome is expected if the treatment has no effect?
The sample mean after the treatment should be close to 80, leading a researcher to fail to reject the null hypothesis.
The results of a hypothesis test are reported as follows in a scientific report: t(38) = -3.13, p < .05. Based on this information, which statement below is not correct?
The sample mean was greater than the hypothesized population mean.
Two samples from the same population both have n = 10 scores with M = 45. If the t statistic is computed for each sample, then what is the relationship between the two t values?
The sample with the smaller variance will produce the larger t statistic.
What is the standard error?
The standard error is the standard deviation of the sampling distribution of a statistic (e.g., t). The standard error tells us about how spread out we'd expect the hypothetical pile of statistic values to be.
Which of the following is a fundamental difference between a t statistic and a z-score?
The t statistic uses the sample variance in place of the population variance
In New York State, the winter months produce higher heating bills and higher levels of depression. Although the numbers show that higher heating bills are related to higher levels of depression, what most likely explains this relationship?
The third-variable problem
A researcher selects a sample and administers a treatment for anxiety to the individuals in the sample. If the sample is used for a hypothesis test, what does the alternative hypothesis ( H 1) put forth about the treatment?
The treatment has an effect on anxiety.
A researcher selects a sample and administers a treatment for anxiety to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis ( H 0) put forth about the treatment?
The treatment has no effect on anxiety.
Which statement below is not consistent with the distribution of sample means.
. The distribution of sample means tends to pile up around the population standard deviation.
The following table shows the results of a two-factor ANOVA. Based on this table, what is the value for η 2 for factor A? Source SS df MS Between 36 3 A 12 1 12 F = 4.00 B 3 1 3 F = 1.00 AxB 21 1 21 F = 7.00 Within 84 28 3 Total 120 31
.125
A sample of n = 9 individuals is selected from a population with µ = 60 and σ = 6, and a treatment is administered to the sample. After treatment, the sample mean is M = 63. What is the value of Cohen's d for this sample?
0.50
Consider that a population is normally distributed with µ= 100 and σ = 6. What is the power of a α = .05, two-tailed hypothesis test with an expected treatment of 2 points and sample size of n = 64?
0.7611
A researcher reports t(5) = +3.00, p < .05 for a repeated-measures research study. The mean sample difference score for the sample was M D = 12. Which of the following is the confidence interval for the population mean difference?
12 ± 10.284
A repeated-measures study using a sample of n = 20 participants would produce a t statistic with df = _____.
19
Dr. Nguyen is studying how amount of sleep influences mood for kindergarteners. A sample of 100 children is selected. Fifty children are allowed to sleep for 11 hours each night. The other 50 children are awoken after 8 hours. After three nights, Dr. Nguyen records the mood for each child and compares the two groups of scores. In this example, how many levels are there for the independent variable?
2
You run an experiment to see how positively people rate three brands of car: Chevrolet, Toyota, Volkswagen. How many pairwise comparisons would there be?
3
A sample of n = 64 scores is selected from a population with µ = 80 with σ = 24. On average, how much error is expected between the sample mean and the population mean?
3 points
A two-factor study with two levels of factor A and three levels of factor B uses a separate group of n = 5 participants in each treatment condition. How many participants are needed for the entire study?
30
How many groups of participants would be needed to partially counterbalance four treatment conditions?
4
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?
5 points
If a repeated-measures study shows a statistically significant difference between two treatments with α = .01, what can the researcher conclude about measures of effect size?
A statistically significant effect does not necessarily indicate that the effect size will be large.
In an experiment, a researcher manipulates people's mood to determine whether changes in mood cause changes in memory performance. However, the researcher is not sure that the manipulation is really causing people's mood to change. In this case, what should the researcher do?
Add a manipulation check by measuring mood.
When should you do post hoc tests?
After a one-way ANOVA that is statistically significant.
Which of the following statements comparing one-tailed with two-tailed hypothesis tests is correct?
All else equal, a less extreme z-score is needed to obtain statistical significance for a one-tailed than two-tailed hypothesis test.
Which of the following statements about the comparison between effect size and power is correct?
As effect size increases, power also increases.
Which of the following is true regarding assumptions underlying the independent-measures t formula for hypothesis testing.
As the discrepancy in sample sizes increases, the assumption that the two populations from which the samples are selected must have equal variances becomes more important.
Which post hoc test approach would be easiest to do without software?
Bonferroni
What is a time-related threat to internal validity for a within-subjects experiment?
Carry-over
A researcher designs a study to determine whether female preschoolers prefer sweetened or unsweetened cereal. The researcher uses a box of sweetened colorful cereal and a box of unsweetened tan colored cereal. The research finds that the group of preschoolers ate more of the sweetened colorful cereal and therefore prefers the sweetened cereal. Which two variables are confounded in this experiment?
Color of the cereal and sweetness of the cereal
Which bit of information is not obtainable from the results of a t-test written up in a statistical report?
Each of these bits of information is obtainable from the results of a t-test written up in a statistical report
Which statement best characterizes a between-subjects experimental design?
Each participant is assigned to one condition of the experiment.
A researcher uncovers that there is a significant interaction between the factor of marital status (i.e., married or non-married) and participant sex (i.e., male or female) regarding well-being among a sample with n = 6 participants in each condition. A researcher decides to compare the difference in well-being between married men and women. The MSwithin treatments from the original two-factor analysis is MSwithin treatments = 1.00. What is the F-ratio for this comparison using the matrix below, which depicts descriptive statistics regarding married participants? __________________________________________________________________________________________ Participant Sex Males Females __________________________________________________________________ n = 6 n = 6 N = 12 M = 4 M = 5 G = 54 T = 24 T = 30
F = 3
A researcher uncovers that there is a significant interaction between the factor of marital status (i.e., married or non-married) and participant sex (i.e., male or female) regarding well-being among a sample with n = 6 participants in each condition. What would the critical value for the F-ratio be for a hypothesis test examining the difference in well-being between married men and women using an alpha level of α = .01?
F = 8.10
Dr. Feliciano is conducting a study of sleep on children's activity level that takes place over several days; however, Halloween falls in the middle of his study, and he notices that on Halloween, the children are especially active during his observation. Which threat to internal validity has confounded this study?
History
A researcher decides to use only participants that weigh between 150 and 160 pounds in an experiment comparing two treatment conditions. For this study, what method is being used to control participant weight?
Holding constant
What is the most common statistical analysis for a single-factor two-group design?
Independent-measures t-test
In a within-subjects research study, factors that change over time, such as history and maturation, can be threats to ____.
Internal validity only
Which characteristic is necessary for an extraneous variable to become a confounding variable?
It must change systematically when the independent variable is changed.
What is the purpose for using a control condition in an experiment?
It provides a baseline to evaluate the size of the treatment effect.
Why is a confounding variable unacceptable in a true experiment?
It threatens internal validity by providing an alternative explanation for the results.
One sample has n = 10 scores and a variance of s 2 = 20, and a second sample has n = 15 scores and a variance of s 2 = 30. What can be concluded about the pooled variance for these two samples?
It will be closer to 30 than to 20.
How does sample variance influence the estimated standard error and measures of effect size such as r 2 and Cohen's d?
Larger sample variance increases the estimated standard error but decreases measures of effect size.
The following data represent the means for each treatment condition in a two-factor experiment. Note that one mean is not given. Which value for the missing mean would result in no main effect for factor B? B1 B2 A1 20 10 A2 40 ?
M = 50
A sample is selected from a normal population with µ = 54 and σ = 8. Which of the following samples would be considered extreme and unrepresentative for this population?
M = 52 and n = 81
Researchers know that excessively low or high exposure to stress during early childhood can become problematic when individuals are exposed to stress as adults. The measurement of exposure to stress during childhood using a well-validated questionnaire forms a normal distribution with µ= 70 and σ = 6. Researchers know that individuals that score in the middle 65% of exposure to stress during childhood tend to respond the best to exposure to stress as adults. Based on this information, for a sample size of n = 16, which range of sample mean values on the stress questionnaire would be expected 65% of the time?
M = 68.605 to M = 71.395
The following data represent the means for each treatment condition in a two-factor experiment. Note that one mean is not given. Which value for the missing mean would most clearly result in an AxB interaction, as well as a simple main effect of factor A regarding those in condition B2? B1 B2 A1 50 30 A2 60 ?
M = 70
The following data represent the means for each treatment condition in a two-factor experiment. Note that one mean is not given. Which value for the missing mean would most clearly result in an AxB interaction? B1 B2 A1 50 30 A2 60 ?
M = 80
If other factors are held constant, which set of sample characteristics is most likely to lead a researcher to reject a null hypothesis stating that µ = 80?
M = 90 for a sample of n = 100
For a repeated-measures study comparing two treatment conditions, a researcher obtains Cohen's d = 0.50 for a sample of n = 4 scores with a variance of s 2 = 16. What is the value of the sample mean difference between conditions?
MD = 2
The following data were obtained from a repeated-measures research study. What is the value of M D for these data? Subject 1st 2nd #1 10 15 #2 4 8 #3 7 5 #4 6 11
MD = 3
The following data represent the means for each treatment condition in a two-factor experiment. What pattern of results is shown in the data? A1 A2 B1 M = 20 M = 20 B2 M = 30 M = 50
Main effects for both factors and an interaction
Which technique provides useful information when there are small changes from one treatment condition to another, when simulations are used or when a placebo is used?
Manipulation checks
In an experiment comparing two treatments, the researcher assigns participants to treatment conditions so that each condition has 10 adults with college degrees and 10 adults with high-school diplomas only. For this study, what method is being used to control participant education level?
Matching
Which of the following describes the effect of an increase in the variance of the difference scores in a repeated-measures design?
Measures of effect size and the likelihood of rejecting the null hypothesis both decrease.
Why do we use alpha = .05, instead of some other number, as the threshold for statistical significance?
Most coherent student answers are acceptable here. The real reason is: tradition. Basically, because that's how scientists have been doing it for decades. That's it. There's nothing magical or inherently meaningful about .05.
Which outcome is possible in a 2 × 2 factorial design?
No main effect for either factor and one interaction
A researcher compares preexisting groups of individuals in which type of study?
Nonequivalent group design
An experiment includes a treatment condition, a no-treatment control, and a placebo control. Which two conditions should be compared to determine the size of the effect that is actually caused by the treatment?
Placebo versus treatment
You want to know if there is a relationship between household income ($ per year), and whether or not there is a grocery store within walking distance of the home (yes/no). You survey many houses. What statistical analysis should you use?
Point-biserial correlation
A researcher comparing depression scores before and after treatment in one group of clients, is using a(n) ____.
Pre-post design
For the following data, what is the value of SS within ? b1: n =5 M =1 SS = 10 b2: n = 5 M = 2 SS = 20
SSwithin = 60
Which post hoc test approach sacrifices the most power?
Scheffé
Which manipulation of the time period between treatment conditions reduces the chances of history influencing the results of a within-subjects experiment?
Shortening
A researcher is interested in the effect of positive affirmations on self-confidence. What is the consequence of adding gender as a factor in the ANOVA?
The MSwithin treatments value will decrease
Assuming all other factors are held constant, if the df value for a two-tailed t-test with α = .05 were increased from df = 6 to df = 20, what would happen to the critical values for t?
The critical values would move closer to t = 0.
Which of the following statements is consistent with hypothesis testing?
The edges of the distribution of sample means are consistent with the alternative hypothesis.
Conceptually, what does the alternative hypothesis of a one tailed repeated-measures research study put forth if a treatment is expected to decrease scores on a questionnaire, relative to pre-test scores on a questionnaire?
There is a decrease in scores after treatment.
Suppose you read an article, by Dr. Blue, reporting one experiment about the effect of X on Y, and the results were p = .040. Now suppose you read a different article, by Dr. Lavender, reporting three experiments about the effect of Z on Y, and the results from all three experiments were p = .060.
There's no single right answer here. Dr. Blue's one experiment yielded results considered statistically significant based on conventional standards (p < .05). None of Dr. Lavender's experiments met that criterion, but they were pretty close to it, AND it replicated (3 times total). Dr. Finley's personal opinion is that Dr. Lavender's article would be more convincing.
What is the effect of decreasing the alpha level (for example, from α = .05 to α = .01)?
This action increases the likelihood of failing to reject H0 and increases the risk of a Type II error.
Which of the following statements correctly describes the effect of increasing the alpha level (for example, from a = .01 to a = .05)?
This action increases the likelihood of rejecting H0 and increases the risk of a Type I error.
A sample has a mean of M = 39.50, a standard deviation of s = 4.30, and produces a t statistic of t = +2.14. For a two-tailed hypothesis test, which of the following is the correct statistical decision for this sample?
This is impossible to determine based on the provided information.
How many independent variables are there in a 2 × 2 × 2 factorial design?
Three
Why might a researcher add a factor when replicating a previously published study?
To see if the treatment effects are the same in a different situation
How many separate groups of participants would be needed for a between-subjects, two-factor study with three levels of factor A and four levels of factor B?
Twelve
How can order effects be measured and evaluated?
Use a factorial design with the order of treatments as a second factor.
For an experiment that compares two treatment conditions with ten scores in each treatment, which design would require the smallest number of participants?
Within participants
Dr. Jones systematically varies the brightness in the laboratory (400, 800, and 1600 lumens) while holding other variables constant, and observes that the participants' activity level decreases as the brightness decreases. This illustrates ____.
a causal relationship between brightness and activity level
A sample is selected from a normal population with a mean of µ = 40. If the sample mean is M = 45, which of the following combinations would make the sample mean an extreme, unrepresentative value for the population?
a large sample and a small population standard deviation
In general, what characteristics of difference scores are most likely to produce a statistically significant t statistic for a repeated-measures hypothesis test?
a large sample size and a small variance
A researcher administers a treatment to a sample of participants selected from a population with µ = 80. If a hypothesis test is used to evaluate the effect of the treatment, which combination of factors is most likely to result in rejecting the null hypothesis?
a sample mean much different than 80 for a large sample
A two-factor research study is used to evaluate the effectiveness of a new blood-pressure medication. In this two-factor study, Factor A is medication versus no medication and factor B is male versus female. The medicine is expected to reduce blood pressure for both males and females, but it is expected to have a much greater effect for males. Which pattern of results should be obtained if the medication works as predicted?
a significant main effect for factor A and a significant interaction
What is indicated by a large variance for a sample of difference scores in the context of a repeated-measures hypothesis test?
an inconsistent treatment effect and a low likelihood of a statistically significant difference between treatment conditions
All else constant, which of the following would not have an effect on the width of a confidence interval?
an increased sample mean
A researcher selects a sample from a population with µ = 30 and uses the sample to evaluate the effect of a treatment. After treatment, the sample has a mean of M = 32 and a variance of s 2 = 6. If Cohen's d is used to measure the size of the treatment effect, which of the following would have no effect on the value of Cohen's d?
an increased sample size
A hypothesis test produces a t statistic of t = +2.19. If the researcher is conducting a two-tailed hypothesis test with α = .05, how large does the sample have to be in order to reject the null hypothesis?
at least n = 13
In an experiment examining the effects of background noise on people's ability to understand a verbal message, one group of participants is given a comprehension quiz after listening to a passage being read to them with no background noise. For comparison, a second group of participants is given a comprehension quiz after listening to a passage being read to them with 60 decibels of conversation as background noise. This is an example of a ____ design.
between-subjects
You run a second experiment about how much SIUE students like Pepsi versus Coke. This time, you randomly give each participant either an unmarked cup of Pepsi or an unmarked cup of Coke, then you ask them to rate how much they like it on a scale of 1-10 (let's treat this DV as interval). What statistical analysis should you use?
between-subjects t-test
A researcher is interested in having as much ability as possible to identify a treatment effect if one really exists. Which of the following strategies should they employ?
change the sample size from n = 25 to n = 100
You want to compare the racial demographics of jury members in St. Louis court trials to the racial demographics of the population of St. Louis, to see if jury panels are really representative of the city's population. What statistical analysis should you use?
chi-square test for goodness of fit
You want to find out if SIUE students have a preference between Pepsi versus Coke. You set up a table on campus (this is after the pandemic), and ask students passing by to participate. (You have an informed consent form, and you got IRB approval ahead of time.) When someone agrees to participate, you randomly give them either an unmarked cup of Pepsi or an unmarked cup of Coke, then you ask if they like it (yes/no). What statistical analysis should you use?
chi-square test of independence
In an experiment, any variable that varies systematically with the treatment conditions and might influence the participants' scores is called a(n) ____ variable.
confounding
In order to establish an unambiguous relationship between two variables, it is necessary to eliminate the possible influence of ____ variables.
confounding
The Pre-post designs are similar to within-subjects designs; however, in a Pre-post design, it is impossible to ____.
counterbalance order of treatments
In an experiment, manipulation of the independent variable requires ____.
creating at least two treatment conditions defined by two different levels of theindependent variable
A research study that evaluates changes in behavior related to age by examining different groups of individuals, with each group representing a different age, is called a(n) ____.
cross-sectional developmental design
A researcher reports t(15) = +0.25, p > .05 for a repeated-measures research study. The mean sample difference score for the sample was M D = 1. Which of the following is the value for Cohen's d?
d = .06
A sample is selected from a population with µ = 46, and a treatment is administered to the sample. After treatment, the sample mean is M = 48 with a sample variance of s 2 = 16. Based on this information, what is the value of Cohen's d?
d = 0.50
A researcher is performing an experiment to determine whether eating chocolate can improve memory. Measurements of memory in this experiment would be the ____ variable.
dependent
A confounding variable is a variable that influences the ____.
dependent variable and varies systematically with the independent variable.
The results of a two-factor analysis of variance produce df = 2, 36 for the F-ratio for factor A and df = 2, 36 for the F-ratio for factor B. What are the df values for the AxB interaction?
df = 4, 36
For an experiment involving 3 levels of factor A and 3 levels of factor B with a sample of n = 8 in each treatment condition, what are the df values for the F-ratio for the AxB interaction?
df = 4, 63
A researcher uses a repeated-measures study to compare two treatment conditions with a set of 20 scores in each treatment. What is the value of df for the repeated-measures t statistic?
df= 19
In an experiment examining the effects of task difficulty (easy/hard) for men and women, the factors are ____.
difficulty and gender
Research indicates the people who suffer from depression also tend to experience insomnia. However, it is unclear whether the depression causes insomnia or the lack of sleep causes depression. This is an example of the ____.
directionality problem
Which statement below is not consistent with the benefits of adding an individual difference variable (i.e., gender) to a single factor (i.e., factor A) ANOVA?
doing so reduces the between treatments variance for the single factor
In a Latin square, ____.
each treatment is administered first in the series for one group of participants
Which of the following elements is always presented last in a statistical report statement describing the results of an independent-measures t test?
effect size
Holding a variable constant prevents a participant characteristic from confounding a study by ____.
eliminating variability in that characteristic
In an experiment, the purpose for manipulating the independent variable is to help ____.
establish the direction of the relationship and help eliminate the third variable problem
Dr. Ramos is interested in studying how indoor temperature can influence people's sleep quality during the summer. A sample of 100 households is selected in which the residents keep their houses at 76 degrees during the summer. The residents wear a monitoring device that measures their sleep cycles for several nights to get baseline readings. Then, 50 of the homes are randomly assigned to the warm temperature condition in which the residents agree to keep their houses at 82 degrees Fahrenheit. In the other 50 houses, the residents agree to keep their houses at 70 degrees. For several nights, Dr. Ramos collects the sleep data for the people living in the houses to see how the residents' sleep patterns have changed. Assuming that the study allows people to use as many or as few blankets as they like, number of blankets would be a(n) ____ variable in the experiment.
extraneous
The critical boundaries for a hypothesis test are z = +1.96 and z = -1.96. If the z-score for the sample data is z = -1.90, which is the correct statistical decision?
fail to reject H0
Even if a treatment has an effect, it is still possible to obtain a sample mean after the treatment that is very similar to the original population mean. Which outcome is likely if this happens?
fail to reject H0 and make a Type II error
A researcher should increase the time between treatment conditions in a within-subjects experiment when he or she wants to decrease the threat of _____.
fatigue
A researcher moves an experiment out of the laboratory and into the real world. This type of research is called a ____.
field study
Under which circumstance can a very small treatment effect still be statistically significant?
if the sample size (n) is very large
Under what circumstances can a very small treatment effect be statistically significant?
if the sample size is large and the sample variance is small
In a between-subjects design, individual differences (participant variables) are a problem because they can ____.
increase variability of the scores
A researcher is forced to collect data from a smaller sample of individuals to test their research hypotheses than originally anticipated. This will have the effect of ______.
increasing the expected distance between M and µ.
Assuming that other factors are held constant, which of the following would increase the likelihood of rejecting the null hypothesis in a hypothesis test using a repeated-measures design?
increasing the sample size
The manipulated variable in an experiment is the ____ variable.
independent
Compared to an independent-measures design, a repeated-measures study is more likely to find a statistically significant effect because it reduces the contribution of variance due to _____.
individual differences
A matched-subjects design attempts to eliminate the problems associated with ____ that are a concern for between-subjects designs and also eliminate the problems associated with ____ that are a concern for within-subjects designs.
individual differences; order effects
For a within-subjects study comparing two treatments, A and B, a researcher expects that practice in the first treatment will improve the participants' scores in the second treatment. If the order of treatments is counterbalanced, then the practice will ____.
influence scores in treatment A for half the participants and scores in treatment B for half the participants
A researcher is evaluating the changes in performance that occur during a six-week training program. Participants are observed at the beginning and at the end of the program and the researcher rates each individual's level of performance. When the researcher's standards for rating performance change from the first observation to the last, then the internal validity of the study is threatened by ____.
instrumentation
Holding a variable constant is a technique for removing one threat to ____ but it can limit the ____ of an experiment.
internal validity; external validity
Researchers often use simulation experiments in an attempt to obtain the ____ of an experiment and still keep much of the ____ of research conducted in the real world.
internal validity; external validity
Within-subjects designs are most useful when individual differences are ____.
large and there are relatively few participants available
The specific treatment conditions that are used in an experiment are called the ____.
levels of the independent variable
In a two-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. Which result(s) would be produced by this pattern of treatment means?
main effects for both factors A and B, and as well as an interaction between factors A and B.
A researcher exposes people to a stressful situation (such as public speaking) to examine the effect of stress on depressed mood. The researcher includes a measure of stress as a ____.
manipulation check
In a within-subjects study that extends over a relatively long time, it is possible that there will be systematic changes in the participants' skills or knowledge during the time of the study. When these changes influence the participants' scores, causing scores at the end of the study to be different from scores at the beginning, the effect is called ____.
maturation
You gather data from a bunch of high school seniors. You want to see if you can predict their SAT scores by using both the number of friends they have on Facebook, and the number of books they read in the past 6 months. What statistical analysis should you use?
multiple regression
For the repeated-measures t statistic, df = _____.
n - 1.
If other factors are held constant, which set of sample characteristics is most likely to produce a statistically significant t statistic?
n = 100 with s2 = 100
A repeated-measures research study and a separate independent-measures research study both produced a t statistic with df = 10. How many individuals participated in each research study?
n = 11 for a repeated-measures research study and n = 12 for an independent-measures research study
The results of a hypothesis test are reported as follows in a scientific report: t(15) = 2.70, p < .05. Based on this report, how many individuals were in the sample?
n = 16
Which of the following samples will have the smallest value for the estimated standard error?
n = 16 with s2 = 16
A researcher is using a two-tailed hypothesis test with α = .05 to evaluate the effect of a treatment. If the boundaries for the critical region are t = ± 2.080, then how many individuals are in the sample?
n = 22
A sample is selected from a normal population with µ = 40 σ = 10. If the sample mean of M = 46 produces a z-score of z = +3.00, then how many scores are in the sample?
n = 25
Consider a normal population with µ = 75 and σ = 10. A sample of at least which size needs to be obtained in order to achieve a standard error of σM = 2.00 or less?
n = 25
A sample with a mean of M = 40 and a variance of s 2 = 12 has an estimated standard error of 2 points. How many scores are in the sample?
n = 3
A researcher conducts a hypothesis test using a sample from an unknown population. If df = 30 for the t-statistic and M = 46 and s 2 = 10, how many individuals were in the sample?
n = 31
A sample obtained from a population with σ = 48 has a standard error of σM = 6. How many scores are in the sample?
n = 64
Does a statistically significant result indicate that the effect has practical significance (i.e., it would actually make a meaningful difference in real life settings)?
no
Dr. Sian varies the amount of a new sedative given to three groups of participants (0, 1, and 2 mg) and then observes the reaction for each group. The 0-mg condition represents the ____ condition.
no-treatment control
You run one more experiment about SIUE student preferences for different kinds of soda. This time, for each participant you give them 4 unmarked cups (in a counterbalanced order). The 4 cups contain: Pepsi, Coke, Dr. Pepper, and A&W Rootbeer. You ask them to rate each cup from 1-10 (let's treat this DV as interval). What statistical analysis should you use?
one-way within-subjects ANOVA
During the first treatment condition of a within-subjects experiment, the participants learn a new skill that helps improve their performance in later treatment conditions. For this study, the internal validity is threatened by ____.
order effects
A random sample of n = 64 scores is obtained from a normal population with µ = 30 and σ = 10. What is the probability that the sample mean will be greater than M = 31?
p = 0.2119
A sample of n = 4 scores is selected from a normal population with a mean of µ = 50 and a standard deviation of σ = 20. What is the probability of obtaining a sample mean less than M = 52?
p = 0.5793
A random sample of n = 25 scores is obtained from a normal population with µ = 30 and σ = 6. What is the probability that the sample mean will be within 2 points of the population mean?
p = 0.9050
For the distribution of sample means for all random samples of a certain size from a population depicted below, what is the probability that a randomly selected sample will have a sample mean less than M = 6?
p = 2/13
Which of the following bits of information is referenced last in an APA formatted statistical report of the results regarding a two-factor ANOVA?
partial eta squared as a measure of effect size
A problem with nonequivalent group designs is that any differences found could be explained by differences in ____.
participant characteristics
Last fall, a state college introduced a one-week study skills course for new freshmen students. At the end of the academic year, the college compared the grades and dropout rate for their freshmen with the corresponding measurements for freshmen at a neighboring state college. This study is an example of a ____.
posttest-only nonequivalent control group design
A sample of n = 16 scores produces a t statistic of t = +2.00. If the sample is used to measure effect size with r 2, which value will be obtained for r 2?
r2 = 0.21
Standardizing procedures, standardizing treatment settings, and limiting individual differences all have the effect of ____.
reducing variance within treatments
Even if a treatment has no effect, it is still possible to obtain an extreme sample mean that is very different from the population mean. Which outcome is likely if this happens?
reject H0 and make a Type I error
If a hypothesis test produces a z-score in the critical region, which decision should be made?
reject the null hypothesis
A researcher conducts a repeated-measures study to evaluate the efficacy of a therapy in treating pain. The researcher examines pain perceptions before and after therapy with a sample of n = 16 participants and obtains a t statistic of t = +1.94. Pain perception levels are less across participants, on average, following treatment. Which of the following is the correct decision for a hypothesis test using α = .05?
reject the null hypothesis with a one-tailed test but fail to reject with a two-tailed test
A researcher expects a treatment to increase the scores for individuals in a population. The treatment is evaluated using a one-tailed hypothesis test, and the test produces z = +2.40. Based on this result, which is the correct statistical decision?
reject the null hypothesis with either α = .05 or α = .01
A researcher conducts a hypothesis test to evaluate the effect of a treatment that is expected to increase scores. The hypothesis test produces a z-score of z = +2.27. If the researcher is using a one-tailed test, which is the correct statistical decision?
reject the null hypothesis with α = .05 but not with α = .01
A hypothesis test involves a comparison of which two elements?
research results from a sample and a hypothesis about a population
Two samples each have n = 4 scores. If the first sample has a variance of s 2 = 10 and the second sample has a variance of s 2 = 6, what is the estimated standard error for the sample mean difference?
s(M1 - M2) = 2
A sample of n = 4 scores has SS = 60. Which is the variance for this sample?
s2 = 20
A sample of n = 7 scores has a mean of M = 65 and an estimated standard error of 2 points. What is the sample variance?
s2 = 28
A sample of n = 25 scores has a mean of M = 40 and a standard deviation of s = 10. What is the estimated standard error for the sample mean?
sM = 2
Which of the following accurately describes the critical region?
sample means that are very unlikely to be obtained if the null hypothesis is true
A sample is obtained from a normal population with µ = 100 and σ = 20. Which of the following samples would produce the most extreme z-score?
sample of n = 100 scores with M = 104 (big m)
Consider a researcher who is exploring new potential treatments for specific forms of cancer. This researcher is extremely focused on avoiding mistakes in concluding that treatments that may very well be effective are ineffective when conducting their research. What should this researcher do?
set a higher alpha level
Consider a researcher who is conducting final clinical trials to validate that a new treatment for anxiety is effective. This researcher is extremely focused on avoiding mistakes in concluding that this new treatment is effective when it really is not when conducting their research. What should this researcher do?
set a low alpha level
A researcher attempts to recreate the real world in the laboratory. This type of research is called a ____.
simulation study
One sample has a variance of s 2 = 10 and a second sample has a variance of s 2 = 6. Which of the following most accurately describes the pooled variance for the two samples?
somewhere between 6 and 10
If participating in treatment A before treatment B causes more fatigue than participating in treatment B before treatment A, then there are ________.
symmetrical order effects
For a repeated-measures study comparing two treatment conditions, a researcher obtains a sample of n = 9 difference scores with a mean of MD = 4 and a variance of s 2 = 36. What is the value for the repeated-measures t statistic for these data?
t = +2.00
It is expected that a treatment will reduce scores on a variable. If α = .05, what is the critical t value for a one-tailed hypothesis test with n = 15?
t = -1.761
On average, which value is expected for the t statistic when the null hypothesis is true?
t = 0.00
If a sample of n = 22 scores is being used to make an 90% confidence interval estimate of the population mean ( µ), which values of t should be used?
t = ±1.721
The results of an independent-measures research study are reported as t(22) = 2.12, p < .05, two tails. For this study, what t values formed the boundaries for the critical region?
t = ±2.074
Which of the following results from a hypothesis test involving the computation of a t-statistic is structured correctly based on standards for presenting hypothesis tests in scientific reports?
t(19) = 2.30, p < .05, r2 = 0.42
Dr. Ramos is interested in studying how indoor temperature can influence people's sleep quality during the summer. A sample of 100 households is selected in which the residents keep their houses at 76 degrees during the summer. The residents wear a monitoring device that measures their sleep cycles for several nights to get baseline readings. Then, 50 of the homes are randomly assigned to the warm temperature condition in which the residents agree to keep their houses at 82 degrees Fahrenheit. In the other 50 houses, the residents agree to keep their houses at 70 degrees. For several nights, Dr. Ramos collects the sleep data for the people living in the houses to see how the residents' sleep patterns have changed. In this study, the independent variable is the ____.
temperature of the houses
What is measured by the numerator of the z-score test statistic?
the distance between the sample mean and hypothesized population mean
In a two-factor analysis of variance, a main effect is defined as _____.
the mean differences among the levels of one factor.
In a factorial design, an interaction between the factors occurs whenever ____.
the mean differences between the cells are not explained by the main effects
Which is the expected value of M?
the mean of the distribution of sample means
Which of the following is consistent with what r 2 represents as a measure of effect size?
the portion of variability in a sample attributable to a treatment effect relative to the total variability in the sample
The concept of nonequivalent groups means ____.
the researcher cannot control which people go into each group and cannot ensure that the groups are equivalent
History, maturation, and instrumentation are especially threatening to studies when _____
the series of treatments extends over a long period of time
A researcher has observed that adults who are more optimistic tend to have a higher level of life satisfaction than adults who are less optimistic. However, the researcher suspects that the apparent relationship may be explained by the fact that some people have positive things happen in their lives, which causes them to be more optimistic and satisfied with their lives compared to people who have bad things happen in their lives and therefore have a more negative outlook on things. This is an example of the ____.
third-variable problem
A researcher measures nicotine cravings in participants each day for one week before and for one week after the researcher begins a program designed to help patients quit smoking. This is an example of a(n) ____ design.
time-series
A researcher assesses the reading level of third-graders on the first of every month for three months prior to administering a new reading program and for three months following the program. This study is an example of a(n) ____.
time-series design
In an experiment, participants are usually assigned to treatments using random assignment. The reason for using random assignment is ____.
to help control extraneous variables
In an experiment, participants are randomly assigned to treatment conditions ____.
to help protect the internal validity of the study
What is the purpose of a one-way ANOVA?
to simultaneously compare the sample means of all the conditions
In a 3 × 4 factorial design, there are ____ main effect(s) and ____ interaction(s) possible.
two; one
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?
use an alpha (α) of .05 instead of .01
When is a researcher at risk of making a Type II error?
whenever H0 fails to be rejected
When is a researcher at risk of making a Type I error?
whenever H0 is rejected
If a sample of n = 4 scores is obtained from a normal population with µ = 70 and σ = 12, what is the z-score corresponding to a sample mean of M = 69?
z = -0.17
A sample of n = 64 scores is selected from a population with µ = 60 and σ = 10. If the sample mean is M = 57, what is the z-score for this sample mean?
z = -2.40
A sample of n = 7 scores is selected from a population with an unknown mean ( µ). The sample has a mean of M = 40 and a variance of s 2 = 63. Which of the following is the correct 95% confidence interval for µ?
µ = 40 ± 7.341
A sample of n = 16 scores is selected from a normal population with σ = 32. If the sample mean of M = 81 produces a z-score of z = -1.75, then what is the population mean?
µ = 95
Which of the following is the correct null hypothesis for a repeated-measures t test?
µD = 0
For a normal population with µ = 60 and σ = 50, the distribution of sample means based on n = 25 will have an expected value of ____ and a standard error of ____.
µM = 60; σM = 10.
Samples of size n = 9 are selected from a normal population with µ = 80 with σ = 18. What is the expected value for the mean of the distribution of sample means?
µM = 80
An instructor is interested in whether frequent feedback in their course to a small sample of students influences student performance. The instructor knows that final class scores are normally distributed with µ = 85 and σ = 6. Which is the alternative hypothesis for this research study?
µfrequent feedback ≠ 85
A researcher is interested in whether a new teaching method influences the public speaking skills of students in an introductory to communications class. The researcher knows that public speaking skills in the class are normally distributed with µ = 10 and σ = 2. Which is the null hypothesis for this research study?
µteaching method = 10
If a treatment is expected to increase scores on a variable for which the mean is expected to be µ = 100, what is the null hypothesis?
µwith treatment < 100
If a treatment is expected to decrease scores on a variable for which the mean is expected to be µ = 50, what is the null hypothesis?
µwith treatment > 50
A sample of n = 16 scores has a standard error of σM = 4. What is the standard deviation of the normally distributed population from which the sample was obtained?
σ = 16
A researcher administers a new treatment to a sample of participants selected from a population with µ = 80. If the researcher obtains a sample mean of M = 88, which combination of factors is most likely to result in rejecting the null hypothesis?
σ = 5 and α = .05
Which symbol is used to identify the standard error of M?
σM
A sample of n = 49 scores with M = 43 is selected from a population with µ = 40 with σ = 21. What is the standard error for the sample mean?
σM = 3
Samples of size n = 9 are selected from a normal population with µ = 80 with σ = 18. What is the standard error for the distribution of sample means?
σM = 6
For a normal population, a sample of n = 9 scores has a standard error of 10. For the same population, a sample of n = 25 scores would have a standard error of _____.
σM = 6.
