Stats exam
Which rule states that when two outcomes are mutually exclusive, the probability that either one of these outcomes will occur is the sum of their individual probabilities?
additive rule
Probability allows us to make predictions regarding:
all
Which of the following is not one of the four steps to hypothesis testing?
identify hypothetical data
The criteria for a decision regarding the value stated in a null hypothesis is set by the
level of significance.
The smaller the level of confidence, the ______ precise the estimate.
more
Using an analysis of regression, the variability in Y that is predicted by X is measured by the ______.
regression variation
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 stat
A researcher measures the extent to which the speed at which people eat (in minutes) predicts calorie intake (in kilocalories). Which factor is the predictor variable in this example?
the speed at which people eat
Each of the following is an example of a binomial distribution, except
the time it takes to complete a driving test
A binomial probability distribution is the distribution of random outcomes for a bivariate or dichotomous random variable.
true
A t test is associated with n - 1 degrees of freedom.
true
A researcher records the strength of a conditioned response among 12 rats in the presence and absence of conditioned cues. If he computes a related-samples t test at a .05 level of significance (two-tailed test), then what are the critical values for this test?
±2.201
The degrees of freedom for a chi-square test for independence test are ______.
(k1 - 1)(k2 - 1)
A point estimate is associated with a high level of confidence that the estimate is in fact equal to the population mean.
False
Increasing sample size will
Increase the power of the decision.
A researcher tests whether job security and life satisfaction are related. In this study, he observes the following frequencies. If he computes a test for independence at a .05 level of significance, then what is the decision for this test?
Job security and job satisfaction are independent.
A researcher concludes that stress levels are higher following a major versus a minor traffic accident (95% confidence interval [CI] 1.86-3.02). If the null hypothesis stated that there would be no difference (null hypothesis: μ= 0), then what is the effect size for this confidence interval?
Ratings of stress shifted between 1.86 and 3.02 points in the population.
If a researcher obtains a null finding, then what is the decision?
They correctly retained the null hypothesis.
When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail, this is called a
Type II error
A researcher selects a sample of 16 women and asks them to rate how important a sense of humor is in someone they want a long-term relationship with. She records scores averaging 1.6 ± 0.8 (M ± SD) on a rating scale from -3 (not important at all) to +3 (very important). Assuming that an average score of 0 is the null hypothesis, test whether or not women find this trait important at a .05 level of significance.
Women found this trait to be important, and this result was significant, t(15) = 8.00, p < .05.
In a sample of 22 participants, suppose we conduct an analysis of regression with one predictor variable. If Fobt = 2.07, then what is the decision for this test at a .05 level of significance?
X does not significantly predict Y.
The correlation coefficient ranges from -1.0 to +1.0, with values closer to ±1.0 indicating ______.
a stronger relationship between two factors
To appropriately interpret the chi-square goodness-of-fit test, it is necessary to compare differences ______.
at each level of the categorical variable
A statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter is called ______.
estimation
The regression equation measures ______.
how far each data point deviates from the line that most closely fits the data
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
The shape of the sampling distribution of the mean is approximately ______, whereas the shape of the sampling distribution of the variance is approximately ______.
normal; positively skewed
The ______ are the range of continuous values containing the score of interest in a binomial distribution
real limits
A researcher records the time (in seconds) it takes participants to respond (by pressing a key) to a familiar and 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.
A researcher selects from a participant pool of four males and six females. He determines that the probability of selecting two male participants is p = .16. Based on this probability, what strategy did the researcher use to sample participants?
sampling with replacement
The normal distribution is symmetrical, which means tha
scores above the mean are distributed the same as scores below the mean.
Which type of error is used to compute the confidence interval for one sample selected from a population with a known variance?
standard error
The test statistic for a related-samples t test makes tests concerning a single sample of
standard error.
The first step to hypothesis testing requires that a researcher
state the hypotheses
A researcher obtains z = 2.04 for a one-sample z test. What is the decision for this test at a .05 level of significance?
to reject the null hypothesis
All z scores above the mean are positive, whereas all z scores below the mean are negative.
true
Complementary outcomes are exhaustive of all possible outcomes.
true
The relative frequency of an outcome is the probability of its occurrence.
true
Suppose you open a new game at the county fair. When patrons win, you pay them $3.00; when patrons lose, they pay you $1.00. If the probability of a patron winning is p = .20, then how much can you expect to win (or lose) in the long run? Hint: You need to compute the expected value of the mean.
win 0.20 cents per play
The correlation coefficient ranges between ______ and ______.
-1, +1
What is the typical level of significance for a hypothesis test in behavioral research? Correct!
.05
A researcher records the following response times to a visual stimulus: 23 ± 3.1 (M ± SD) s. Assuming these data are normally distributed, what is the probability that participants responded in 20 s or less?
.1660
A researcher selects a sample of 110 participants and computes the following phi correlation coefficient: rϕ = .31. What is the value of χ2?
10.57
A researcher reports the following equation for a best-fitting straight line to a set of data points: . Which value is the y-intercept?
3.24
A researcher estimates the 95% CI for a sample with a mean of M = 3.26 and a standard error (σM) of 0.91. What is the upper confidence limit for this interval?
5.04
A researcher compares the frequency of participants who sleep primarily on their stomach, back, or side during the night. What is the critical value for a chi-square goodness-of-fit test at a .05 level of significance?
5.99
A researcher computes a 2 × 4 chi-square test for independence. What are the degrees of freedom for this test?
8
If the standard deviation of a probability distribution is 9, then the variance is ______.
81
The expected value of a random variable can be thought of as a "long-term" mean.
true
The standard deviation and the mean can equal 0 in a data set that is normally distributed.
false
The sample space is equal to the total number of random outcomes possible for a random variable.
true
The smaller the level of confidence, the more precise the estimate.
true
In a normal distribution, 50% of all data:
all
Which of the following proportions is largest in a zdistribution?
The proportion of area between z = +1 and z = -1.
Hypothesis testing is also called
significance testing.
State the critical value(s) for the following two-tailed t test at a .05 level of significance: t(∞).
±1.645
What is the z score for scores in the top and bottom 2.5%?
±1.96
What is the z score for scores in the bottom 10%?
-1.28
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24).
-1.711
A researcher determines that students study an average of 80 ± 20 (M ± SD) min/week. Assuming these data are normally distributed, what is the z score for students studying 60 min/week? You Answered
-1.0
A researcher computes a 2 × 2 chi-square test for independence. What is the critical value for this test at a .05 level of significance?
3.84
A researcher records the following assessment data: 42 ± 6 (M ± SD). The researcher only wants to sample participants scoring in the top 20% of this assessment. What is the cutoff score for the top 20% in this example?
47.04
A researcher estimates the 90% CI for a sample with a mean of M = 8.9 and a standard error (σM) of 2.1. What is the confidence interval at this level of confidence?
90% CI 5.5, 12.4
Which of the following is NOT a characteristic of probability?
Probability is most useful for describing fixed events.
The correlation coefficient is used to measure the ______ and ______ of the linear relationship between two factors.
STRENGTH AND DIRECTIN
A distribution of z scores is distributed in what type of unit of measurement?
Standard deviation units
The t distribution is similar to the z distribution, except
all
Which of the following is an example of a nonparametric test?
chi-square test
As sample size increases, the standard error of the mean
decreases.
Many nonparametric tests are called ______ because they make no assumptions regarding the shape of the distribution in the population.
distribution-free tests
A measure of the size of an effect in a population is called
effect size
A chi-square goodness-of-fit test shows that the frequencies observed equal those that were expected. Hence, the value of the test statistic is ______.
equal to 0
The mean of the sampling distribution of sample means is
equal to the population mean.
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.
The mean of a probability distribution is called the
expected value of the mean and mathematical expectation.
A researcher selects a sample of 49 participants from a population with a mean of 12 and a standard deviation of 3.5. What is the probability of selecting a sample mean of 13 or larger from this population?
less than .10
Probability ranges between 0 and 1 and is never negative
true
A researcher records the number of distracters (such as noises) that preschool-aged children ignore while watching a popular Sunday morning cartoon show. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
one-sample t test
A researcher measures the extent to which years of marriage predict perceptions of forgiveness. Which factor is the criterion variable in this example?
perceptions of forgiveness
What is the implication for the tails of a normal distribution being asymptotic?
that extreme scores are possible in the tails of a normal distribution
As a general rule, the larger the degrees of freedom for a chi-square test, ______.
the larger the critical value will be
If the expected frequencies are equal to observed frequencies for a chi-square test for independence, what do we conclude?
the test statistic value is equal to 0
The "left-over" or remaining variation attributed to error in an analysis of regression is called residual variation.
true
The asymptotic tails in a normal distribution represent the possibility of outliers in a data set.
true
The binomial probability distribution is distributed with μ = np and σ = .
true
Which type of error is used to compute the confidence interval for one sample selected from a population with an unknown variance?
estimated standard error
In a normal distribution with 2.2 ± 4.1 (M ± SD), a researcher can appropriately conclude that most scores occurred above the mean.
false
Which of the following is used to determine the linear equation that best fits a set of data points?
method of least squares
You read about a study testing whether night shift workers sleep the recommended 8 hr/day. Assuming that the population variance of sleep (per day) is unknown, what type of t test is appropriate for this study?
one-sample t test
What are the two decisions that researchers can make in hypothesis testing?
retain or reject the null hypothesis
A chi-square goodness-of-fit test shows that the frequencies observed fit well with those that were expected. Hence, the decision was to ______.
retain the null hypothesis
The degrees of freedom associated with regression variation are equal to ______.
the number of predictor variables
Two outcomes are said to be mutually exclusive when
the probability of the two outcomes occurring together is equal to zero (p = 0).
Which of the following best describes the goal of estimation?
to narrow in on the true population mean by defining limits within which it is likely to be contained
The formula for the chi-square test measures the size of the discrepancy between observed and expected frequencies.
true
A professor gives an exam in which the mean score is 78 points. She gives another exam to test whether or not scores change. In this example, the null hypothesis is
μ = 78
Suppose that the probability that any child of alcoholic parents becomes alcoholic is p = .16. Assuming independent outcomes, the probability that two children of alcoholic parents will be alcoholic equals ______.
.03
In a sample of 20 participants, a researcher estimates the 95% CI for a sample with a mean of M = 5.4 and an estimated standard error (SM) of 1.6. What is the upper confidence limit for this interval?
8.8
The chi-square test is an example of a parametric test.
false
The coefficient of determination is a measure of significance.
false
The degrees of freedom for the chi-square test for independence are k - 1.
false
The distribution of probabilities for each outcome of a random variable that sums to 1.00 is called a
probability distribution.
Given the following values: μ = 10, M = 8, σM = 0.5, conduct a one-sample z test at a .05 level of significance. What is the decision for a two-tailed test?
to reject the null hypothesis
Below is the probability distribution for the number of times students had to take the same exam before passing it. If a student must pass the exam in two tries or less to pass the class, then what is the probability of passing the class? x1234p(x)0.400.400.100.10
.80
Below is the probability distribution for random variable x. What is the probability of at least a score of 2 in this distribution? x. 1 2 3 p(x)0.18. 0.42. 0.40
.82
A t test is associated with N degrees of freedom.
false
A sampling distribution is a distribution of all sample means or sample variances that can be obtained in samples of a given size from the same population.
true
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1 - M2 = 8.8 and an estimated standard error for the difference (SM1 - M2) of 1.8. What is the upper confidence limit for this interval?
11.2
A researcher records the following times (in seconds) that it took a group of students to complete an exam: 18 ± 2 (M ± SD) min. How long did it take 80% of students to complete the exam?
19.68 min
A researcher reports the following results for a chi-square test: χ2 () = 5.39, p < .05 (V = 0.22). What is the maximum number of levels that an independent variable could have had?
2
A researcher selects a sample of 80 people and records the frequency of participants choosing a low, moderate, or high calorie dessert in a buffet. What are the degrees of freedom for this chi-square goodness-of-fit test?
2
An article states that a sample of 40 participants took 12 ± 2.3 (M ± SEM) seconds to complete a cognitive assessment. Which value is the standard error of the mean?
2.3
A researcher obtains z = 3.98 for a one-sample z test. If her decision is to retain the null hypothesis, then what do you know about her decision?
Her decision resulted in a Type III error.
A researcher states that the average child acquires 2.6 taste aversions in his or her lifetime. This is an example of a point estimate.
true
A sample mean is not always equal to a population mean.
true
Correlation does not show causation.
true
The sampling distribution of the mean is a distribution of all the possible samples of a particular size that can be selected from a given population.
true
The z statistic is a z transformation for a distribution of sample means.
true
Which of the following is a possible value for the standard deviation of a normal distribution?
.5
In a sample of 12 participants, a researcher estimates the 80% CI for a sample with a mean of M = 22.3 and an estimated standard error (SM) of 4.7. What is the confidence interval at this level of confidence?
80% CI 15.9, 28.7
The sample mean is an unbiased estimator of the population mean only when we divide SS by df.
false
The total area under a normal curve increases as the standard deviation increases.
false
There is no difference between a point estimate and an interval estimate.
false
It happens to be the case that the standard error of the sampling distribution of sample means
is minimal
Each of the following is an advantage for using the related-samples design, except
it increases the variability measured in a study.
The degrees of freedom for a chi-square goodness-of-fit test are ______.
k - 1
The larger the level of confidence, the ______ precise the interval estimate.
less
Scores far from the mean are located in the ______ of a normal distribution.
tails
A null finding is a decision to retain a null hypothesis that is correct.
true
A probability can be stated as a proportion.
true
A researcher reports the following result for a two-tailed test at a .05 level of significance, t(30) = 2.020, and correctly decides to retain the null hypothesis.
true
If a complimentary outcome has a 1 in 10 chance of occurrence, then the probability of that outcome is p = .10.
true
If r = .25, then the coefficient of determination is .06.
true
In a normal distribution, the probability of a score above -1.0 SD is equal to the probability of a score below +1.0 SD.
true
Linearity is the assumption that the best way to describe a pattern of data is using a straight line.
true
Nonparametric tests do not make inferences about population parameters, although these tests can be used to test hypothesized relationships in the population.
true
Normality, random sampling, and independence are all assumptions for the one-sample t test.
true
Outliers can change both the direction and strength of a correlation coefficient.
true
What are the degrees of freedom for the related-samples t test?
(nD - 1)
A researcher must know the population variance in order to compute a t test.
False
Which of the following best describes the p value.
It is a conditional probability
A researcher wants to know the probability of being named on the honor roll from a population where 8% of students are on the honor roll. If the researcher selects a sample of 400 students, then what is the mean number of students expected to be on the honor roll? Hint: This is a binomial distribution, where p = 0.08 and q = 0.92.
32
A researcher reports with 90% confidence that 31% to 37% of Americans believe in ghosts. What is the point estimate for this interval?
34%
A researcher conducts two t tests. Test 1 is a two-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a two-tailed test with a larger sample size at a .05 level of significance. What do you know about the degrees of freedom for each test?
Test 2 is associated with larger degrees of freedom.
A researcher computes a 2 × 3 chi-square test for independence. What is the critical value for this test at a .05 level of significance?
5.99
A researcher records the frequency of participants selecting one of four new slogans for an advertising campaign. If it was expected that among 200 people polled there would be no preference for any one slogan, then what was the expected frequency for each slogan.
50 people
To compute the expected frequencies for a chi-square test for independence, we use which of the following formulas?
(row total × column total)/grand total
If SSXY = -16.32 and SSX = 40.00 for a set of data points, then what is the value of the slope for the best-fitting linear equation?
-0.41
A researcher determines that students are active about 60 ± 12 (M ± SD) min/day. Assuming these data are normally distributed, what is the z score for students being active 48 min/week?
-1.0
What is the z score for scores in the bottom 5%?
-1.645
The standard normal distribution is normally distributed with a mean of ______ and a variance of ______.
0; 1
A researcher selects a sample of size 6 from a population of size 10. How many possible samples of this size can be selected using theoretical sampling?
1,000,000
What is the central limit theorem?
It explains that a sampling distribution of possible sample means is approximately normally distributed, regardless of the shape of the distribution in the population.
What is a key distinction between parametric tests and nonparametric tests in terms of scales of measurement?
Parametric tests are used for interval and ratio data, whereas nonparametric tests are used for nominal and ordinal data.
A researcher asks participants to taste each of three meals and to choose the one they like best. The same foods are in each meal, expect for the calorie total of the meal (which is low, moderate, or high calorie). Based on the observed frequencies given below, what is an appropriate conclusion for this test at a .05 level of significance?
Participants liked the high calorie meal more than was expected.
A researcher selects two samples of 64 participants each. In the first sample, the population mean was 10 and the variance was 16. In the second sample, the population mean was 25 and the variance was 9. Which sample will be associated with a larger standard error of the mean?
Sample 1.
A researcher determines that the probability of winning a new game is p = .32. Assuming winning and losing are mutually exclusive events, what is the probability of winning and losing the new game?
This outcome is not possible, p = 0.
A t statistic estimates the standard error by using the sample variance to approximate the population variance.
True
One step to hypothesis testing is to set the criteria for a decision.
True
Rejecting a true null hypothesis is a Type I error.
True
The alpha level is the likelihood of committing a Type I error.
True
The level of significance in hypothesis testing in the behavioral sciences is typically set at .05.
True
The null hypothesis and alternative hypotheses are statements about parameters in the population.
True
A researcher directly controls for the probability of a ______, but does not directly control for the probability of a ______.
Type I error; Type II error
Regardless of the distribution of the population, the sampling distribution of sample means will be approximately normally distributed. What characteristic of the mean explains this?
central limit theore
Which of the following is a statistical procedure used to test hypotheses about the discrepancy between the observed and expected frequencies in two or more nominal categories?
chi-square test
When the sum of the probabilities of two outcomes is exhaustive of all possible outcomes, these outcomes are referred to as
complementary
The one-sample z test is a hypothesis test used to test hypotheses
concerning a single population with a known variance.
When the probability of one outcome changes depending on the occurrence of the second outcome, these outcomes are referred to as
conditional
Which of the following words best describes certainty?
confidence
A researcher visits a population of 1,200 local residents to determine the proportion of local residents who support a new smoking ban. In this case, the sample space is
equal to the population of 1,200 local residents
Which of the following is an assumption for the two-independent-sample t test, but not the one-sample t test?
equal variances
A key difference between a t statistic and a z statistic is that the standard error is ______ to compute a t statistic.
estimated
Which type of sampling is most often applied by researchers in the behavioral sciences?
experimental sampling
A 2 × 2 chi-square test for independence has 4 degrees of freedom.
false
A binomial probability distribution is constructed for random variables that have at least two possible outcomes.
false
A chi-square goodness-of-fit test with three levels of a categorical variable will have 3 degrees of freedom.
false
As the standard error increases, the precision of an estimate also increases.
false
In a normal distribution, the mean can only take on positive values.
false
In a normal distribution, the probability of a score above the mean is larger than the probability of a score between first standard deviation above and below the mean.
false
It is appropriate to use the normal approximation of the binomial distribution with a sample of 100 participants, where p = .07 and q = .93.
false
Linear regression is used to measure the extent to which a criterion variable causes changes in a predictor variable.
false
Parametric tests are often called distribution-free tests.
false
The estimation formula for the related samples t is MD ±t(sM1 - M2).
false
The multiplicative rule is used to define mutually exclusive outcomes.
false
The probability of an outcome can be any positive value.
false
The probability of an outcome is particularly useful for predicting the likelihood of fixed events.
false
The regression line is not always the best fitting straight line to a set of data points.
false
Two outcomes are mutually exclusive when the probability of one outcome is equal to the probability of the second outcome.
false
When k = 3, then the critical value for a chi-square goodness-of-fit test is 7.81.
false
Which of the following is recorded using a chi-square goodness-of-fit test and a chi-square test for independence?
frequency observed and frequency expected
A researcher computes a test statistic and finds that the pvalue for this test is .03. What does this result mean?
here is a 3% likelihood of obtaining the test statistic value, if the null were true.
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 observed frequencies can be summarized, ______.
in a table in a figure in the main tex
If the value stated by a null hypothesis is ______ the confidence interval, then the decision would have likely been to retain the null hypothesis.
inside
In a hypothetical job field, 10% of workers are promoted within their first year of employment. For this hypothetical job field, what is the probability that exactly 25 workers were promoted in their first year in a random sample of 200 workers? Hint: This is a binomial distribution, where p= .10 and q = .90.
less than 5%
Which of the following is a type of related-samples design in which different participants are observed in each group, but treated statistically as if they are the same persons in each group?
matched-samples design
Which rule states that when two outcomes are independent, the probability that these outcomes occur together is the product of their individual probabilities?
multiplicative rule
The degrees of freedom associated with residual variation are equal to ______.
n - 2
A correlation coefficient can ______ demonstrate cause.
never
Two normal distributions are observed. The first distribution has a mean of 12 and a standard deviation of 2. The second distribution has a mean of 0 and a standard deviation of 2. For which distribution will the z score for the mean be larger?
none, the z score will be the same
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.
The probability of a student attending every college class is p = .26. The probability of a student attending every college class and earning an A is p = .22. Hence, the probability of a student earning an A, given that he or she attends every college class, is ______.
p = .85
The probability of a college student being employed is p = .35. The probability of a student being employed and dropping out of college is p = .20. Hence, the probability of a student dropping out of college, given that he or she is employed, is ______.
p=.57
The proportion or fraction of times an outcome is likely to occur is referred to as
probability.
A local ice cream shop wants to see if they should promote a new swizzleberry swirl or creamsicle flavored drink. In order to determine which one to promote, they took a sample of 80 patrons and asked them to choose which they preferred. The one that is significantly preferred over the other (at a .05 level of significance) will be promoted. It is expected that an equal number of patrons will choose each flavor. Based on the observed frequencies given below, what is the decision for this test?
promote the creamsicle flavored drink
In hypothesis testing, a researcher can never
prove that his or her hypothesis is correct
Which of the following indicates the strongest correlation?
r = -0.90
A researcher compares the height of male executives in the United States to the average height of males (μ = 67 in.). He determines that the average height of male executives is 70 in. (95% confidence interval [CI] 68-72).Based on this result, what would the decision have been for a hypothesis test?
reject the null hypothesis
The correlation coefficient measures the extent to which changes in one factor are ______ in a second factor.
related to changes
Using an analysis of regression, the variability in Y that is associated with error is measured by the ______.
residual variation
A researcher conducts a chi-square goodness-of-fit test in which k = 3 and χ2 = 4.32. What is the decision for this test at a .05 level of significance?
retain the null hypothesis
The total number of possible outcomes for a random variable is referred to as
sample space
The estimated standard error in the t statistic uses the ______ to estimate the ______ when the population variance is unknown.
sample variance; population variance
Outliers can change the ______ of a correlation.
strength
A researcher conducts two chi-square tests. The 2 × 2 chi-square was χ2 = 3.92. The 2 × 3 chi-square was χ2 = 5.92. Which chi-square test resulted in a decision to reject the null hypothesis at a .05 level of significance?
the 2 × 2 chi-square
The coefficient of determination is mathematically equivalent to η2.
true
The estimated standard error is used in the formula to estimate the population mean for the one-sample t.
true
The estimation formula for the one-sample t is M ± t(sM).
true
The estimation formula for the one-sample z is M ± z(σM).
true
The expected value of a random variable is the mean of a probability distribution.
true
The least certain, but most precise, estimate is a point estimate.
true
The mean of a binomial distribution is the product of the number of trials (n) times the probability of the outcome of interest on an individual trial (p).
true
The mean, median, and mode are all located at the 50th percentile in a standard normal distribution.
true
The multiplicative rule is used for independent outcomes.
true
The population variance must be known to estimate the population mean for the one-sample z.
true
The predictor variable is a known value that is used to predict the value of another variable.
true
The probability that a participant is married is p(M) = .60. The probability that a participant is married and "in love" is p(M∩L) = .46. Thus, the probability that a participant is in love, given that the participant is married, is p = .77.
true
The standard error of the mean is the standard deviation in a sampling distribution of sample means.
true
The test statistic is the same for a chi-square goodness-of-fit test and a chi-square test for independence.
true
To estimate the population mean for the two-independent-sample t, the sample size must be known.
true
To summarize the chi-square test, report the test statistic, the degrees of freedom, and the p value.
true
Variance is not computed using the chi-square tests.
true
A professor compares final exam scores in his psychology class to final exam grades in another comparable professor's class. Assuming that the population variance of exam scores is unknown, what type of t test is appropriate for analyzing differences between these classes?
two-independent-sample t tes
A researcher records differences in ratings of emotion among participants watching either a drama or a romance film. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
two-independent-sample t test
A researcher tests whether levels of education and income levels are related. In this study, he observes the following frequencies. If he computes a chi-square test for independence at a .05 level of significance, then what is the decision for this test?
Education and income level are related.
______ allows researchers to describe (1) how far mean scores have shifted in the population or (2) the percentage of variance that can be explained by a given variable.
Effect size
A researcher computes a z statistic and obtains z = 2.10. If this were a one-tailed (lower-tail critical) test, then the decision would be to reject the null hypothesis.
False
A researcher tests a hypothesis to prove whether or not his or her hypothesis is correct.
False
For a set of data with 25 ± 2.5, at least 95% of scores fall between 20 and 30.
true
A researcher records the following number of birdcalls made during an experimental session with robins: 7.2 ± 0.6 (M ± SD). Assuming these data are normally distributed, what is the probability that robins made more than nine birdcalls during this experimental session?
.0013
A researcher selects a sample of 25 participants from a population with a mean of 10 and a standard deviation of 5. What is the probability of selecting a sample mean that is at least two standard deviations larger than the population mean?
.0228
A researcher measures the following correlation: r = -.21. What is the value of the coefficient of determination?
.04
A researcher records the following data for the number of bids made on a sample of items sold at an auction. Based on the table, what was the probability that an item had seven bids made on it?
.25
A researcher records the number of job openings among small businesses. She finds that the probability that a small business has 0 job openings is p = .22; 1 job opening is p = .45; 2 job openings is p = .08; and 3 job openings is p = .25. What is the probability that a small business has at least 2 job openings? You Answered
.33
A researcher reports the following equation for a best-fitting straight line to a set of data points: . Which value is the slope?
.48
A professor records the grades for his class students. He finds that the probability that a student earns an A is p = .14; earns a B is p = .36; earns a C is p = .32; earns a D is p = .10; and earns an F is p = .08. What is the probability that a student earns a B or better in this class?
.50
A therapist goes through her records and finds that 200 of her 400 patients showed significant improvement in mental health over the past year. Hence, the probability of her patients showing significant improvement in mental health is ______.
.50
A researcher measures the relationship between narcissism and willingness to help. If SSXY = 240, SSX = 320, and SSY = 410, then what is the value of the correlation coefficient?
.66
In a game, the probability of winning money is p = .16, the probability of losing money is p = .54, and the probability of breaking even is p = .30. What is the probability of winning or losing money in this game?
.70
A researcher records the following body mass index (BMI) scores for a group of participants: 28.4 ± 1.6 (M ± SD). Participants who score between 25 and 30 on this scale are categorized as overweight. What percentage of participants fell in this overweight category?
.8247
A counselor records the number of disagreements (per session) among couples during group counseling sessions. If the number of disagreements is distributed normally as 4.4 ± 0.4 (M ± SD) disagreements, then what proportion of couples disagree at least four times during each counseling session?
.8413
A researcher measures the number of tasks completed by participants during a 5-min multitasking session. If the number of tasks completed is distributed normally as 6.3 ± 1.0 (M ± SD) tasks, then what is the probability that participants completed less than eight tasks?
.9554
A researcher determines the probability that a research study will reveal something new is p = .80. What is the probability that the study will reveal something new or not reveal something new?
1.00
A researcher estimates the 95% CI for a sample with a mean of M = 3.26 and a standard error (σM) of 0.91. What is the lower confidence limit for this interval?
1.48
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
What is the z score for scores in the top 2.5%?
1.96
A news poll showed that voters had no preference for either of three candidates. In this example, the probability of a vote for, say, Candidate A equals ______.
1/3
A gambler rolls a 3 with one roll of a single fair die. Given that the die was six-sided, what was the probability of rolling a 3 with one roll?
1/6
If the variance of a probability distribution is 121, then the standard deviation is ______.
11
In a sample of 26 participants, a researcher estimates the 90% CI for a sample with a mean of MD = 0.6 and an estimated standard error for the difference scores (SMD) of 1.1. What is the upper confidence limit for this interval?
2.5
A researcher reports that the probability of a college student living on campus is p = .38. If a small local college has 2,000 students enrolled, then what is the standard deviation of college students living on campus? Hint: This is a binomial probability distribution.
21.7
A researcher records the following times (in seconds) that it took a group of mice to complete a maze: 23 ± 4.1 (M ± SD). The top 10% of mice finishing with the fastest times will be placed in a "maze bright" group. What is the cutoff time to be placed in this group?
28.25 s
A researcher computes a 2 × 4 chi-square test for independence. What are the degrees of freedom for this test?
3
A researcher selects a sample of 100 participants from a population with a mean of 38 and a standard deviation of 20. About 68% of the sample means in this sampling distribution should be between a sample mean of
36 and 40
A researcher reports the following results for a chi-square test for independence: χ2 (1) = 5.39, p < .05 (V = .22). How many groups were observed?
4
In a sample of 18 participants, a researcher estimates the 80% CI for a sample with a mean of M1 - M2 = 8.8 and an estimated standard error for the difference (SM1 - M2) of 1.8. What is the lower confidence limit for this interval?
6.4
What does it mean to say that the sample mean is an unbiased estimator of the population mean?
If we select a sample at random, then on average we can expect the sample mean to equal the population mean.
A researcher wants to know the probability of selecting a student athlete from a school population where 5% of students are athletes. If the researcher selects a sample of 120 students, is it appropriate to use the normal approximation of the binomial distribution to estimate this probability?
No, because np is less than 10
A parent decides to reward her child if he eats an average of at least five bites of his vegetables at dinner during the first week. She finds that her child ate 4 ± 0.8 (M ± SD) bites per meal for the first week. Assuming these data are normally distributed, should this parent reward her child?
No, because the z score for 5 bites is greater than 0.
A researcher records the number of mistakes made during a memory skills task. He finds that the probability that participants in this study made 0 mistakes is p = .22; made 1 mistake is p = .30; made 2 mistakes is p = .16; made 3 mistakes is p = .12; and made 4 or more mistakes is p = .25. Is this probability distribution accurate?
No, the probability distribution does not sum to 1.0.
A researcher finds that the mean difference in productivity between employees working the morning shift (n = 16) and the night shift (n = 10) is 5.0 units, and the estimates standard error for the difference is 2.7 units. If the null hypothesis states that there is no difference in productivity, then is this result significant at a .05 level of significance for a two-tailed test?
No, this result is not significant.
What is the key assumption for a chi-square goodness-of-fit test?
Observed frequencies are independently recorded in each cell.
For mutually exclusive outcomes, one or the other outcome can occur (Outcome A or Outcome B), but not both outcomes (Outcome A and Outcome B).
true
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= 1.00, or the area to the left of z = -1.00.
The first area is bigger
A researcher reports that college students consume an average of 3.6 alcoholic drinks per week. What is the interval estimate in this example?
The interval estimate is not given.
Which of the following is a characteristic of confidence intervals?
The less certain an estimate, the more precise the estimate, and the more certain an estimate, the less precise the estimate.
A researcher measures the following correlation between cups of coffee consumed daily and daily work schedule. Which description best explains the relationship between these two factors?
The more a person works, the more coffee he or she tends to drink.
Which of the following statements regarding the null hypothesis is true?
The null hypothesis always makes statements about a population parameter.
To compute a one-sample 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 must be known.
Which of the following explains why point estimation can be a useful procedure to estimate a population mean?
The sample mean is equal to the population mean on average and the sample mean is an unbiased estimator of the population mean.
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
A statistical procedure used to describe the strength and direction of the linear relationship between two factors is called ______.
a correlation
For the same data, increasing the certainty of an estimate will result in a less precise estimate.
true
Suppose that a researcher selects a sample of 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 theoretical distribution that evenly distributes data around the mean, median, and mode is called the
all
Because the sampling distribution of sample means is normally distributed, we can use the z transformation formula to find probabilities. Which of the following gives the appropriate notation for this formula?
all
If the value of the test statistic is in the rejection region, then
all
Linear regression describes the extent to which ______ predicts ______.
all
Researchers state a level of significance in terms of an alpha level. The alpha level indicates
all
Which of the following is an appropriate step for the normal approximation of the binomial distribution?
all
Which of the following is an assumption for computing any type of independent-sample t test?
all
Computing a one-sample t test is appropriate when
all of the above
By definition, the probability of an outcome or event is
all of these
The confidence interval for samples selected from one or two populations with an unknown variance is computed using critical values from the t table. This is true for which of the following types of samples?
all of these
The probability of committing a Type I error is stated by ______; the probability of committing a Type II error is stated by ______.
alpha; beta
Most behavior is believed to ______ a normal distribution.
approximate
The method of least squares is used to determine the ______ straight line to a set of data points.
best-fitting
A distribution of probabilities for random outcomes of a bivariate or dichotomous random variable is called a
binomial probability distribution.
Each of the following statements are true, except that
the larger the sample size, the larger the standard error.
The power of the decision-making process is
the likelihood of rejecting a false null hypothesis
Which of the following is the numerator of the test statistic for the related-samples t test?
the mean difference observed minus the mean difference stated in a null hypothesis
To compute a two-independent-sample 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 pooled population variance
The normal distribution has all of the following characteristics, except that
the total area under the curve is greater than 1.0.
A professor finds that the average SAT score among all students attending his college is 1150 ± 150 (μ ± σ). He polls his class of 25 students and finds that the average SAT score is 1200. Suppose he computes a one-sample ztest 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
Given the following values: μ = 6.0, M = 7.6, n = 36, σ = 6, conduct a one-sample z test at a .05 level of significance. For a one-tailed test, upper-tail critical, what is the decision?
to retain the null hypothesis
A t distribution with infinite degrees of freedom is a z distribution.
true
A z score for the mean in a normal distribution is always equal to 0.
true
The unit of measurement distributed along the x-axis of a standard normal distribution is referred to as a
z score.
The confidence interval for one sample selected from a population with a known variance is computed using a critical value for which type of test?
z test
