Exam #2 Stats
Which figure below depicts data from a study on child play behavior with a smaller value for error variance?
Figure A
Is a one-sample t test reported differently for one-tailed and two-tailed tests?
No the same values are reported
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 () of 1.8. What is the upper confidence limit for this interval?
6.4
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
Eta-squared is computed ______ for the one-sample, and the two-independent-sample t tests.
similarly
Which of the following summarizes a t test that was significant and associated with a large effect size?
t(12) = 2.95, p < .05, d = .82
Experimental research is typically conducted using a sampling strategy in which __
the same participants can never be selected twice in the same sample set
A researcher obtains z = -6.45. What is the decision for a one-tailed test, upper-tail critical, at a .05 level of significance?
to retain the null hypothesis
A researcher directly controls for the probability of a ______, but does not directly control for the probability of a __
Type I error; Type II error
A sampling distribution of the sample mean or variance is __
a distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population
In hypothesis testing, a researcher's decision _
all of the above
Which of the following is an assumption for computing any type of independent sample t test?
all of the above
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 of these
Computing a two-independent-sample t test is appropriate when _
all of these
Which of the following is a scenario in which increasing sample size will increase power _
all of these
The sampling distribution of the mean and the sampling distribution of the variance (when dividing SS by n - 1) ___
are both unbiased estimators
State the critical value(s) for the following two-tailed t test at a .05 level of significance: t().
both b and c
A researcher reports that mean ratings of liking for some food are 0.8 ± 2.4 (M ± SD). If the null hypothesis was that the mean equals 0, then what is the effect size for this test using estimated Cohen's d?
d= .33; medium effect size
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 results in a type III error
Is a one-sample z test reported differently for one-tailed and two-tailed tests?
no, the same values are reported
A measure of the size of an effect in a population is called ___
probability
In Step 2 of hypothesis testing, researchers state a level of significance to minimize the probability of ___
rejecting a true null hypothesis
Which of the following summarizes a t test that was significant and associated with a large effect size?
t(12)= 2.95, p< .05, d= .82
Which of the following allows researchers to use the standard normal distribution to estimate the probability of selecting sample means?
the central limit theorem
A researcher reports that scores were higher than the mean in the population, z = 1.60, p = .05 (d = .14). If this was a test at a .05 level of significance, then what value must be incorrectly reported?
the p value
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
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
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 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
A researcher selects a sample of size 4 from a population of size 6. How many possible samples of this size can be selected using experimental sampling?
15
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 () of 1.6. What is the upper confidence limit for this interval?
2.1
An article states that a sample of 40 participants took 12 ± 2.3 (M ± SEM) s to complete a cognitive assessment. Which value is the standard error of the mean?
2.3
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.
A researcher conducts a study, but has low power to detect an effect. Which of the following is one way in which the research can increase power?
increase the sample size
The one-sample z test is a hypothesis test used to test hypotheses __
concerning a single population with a known variance
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24).
(about) 1.711
The t distribution is similar to the z distribution except
All of these
State the critical value(s) for the following two-tailed t test at a .05 level of significance: t().
Both b and c
Which measure of effect size is most commonly reported with a t test?
Cohen's d
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
A researcher reports a significant effect in some population. If he computes both an eta-squared and an omega-squared effect size estimate, then which estimate will be the largest?
Eta-squared
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 population mean
Increasing sample size will
Increase the power of decision
Which of the following best describes the p value
It is conditional probability
As sample size increases, the standard error of the mean _
decreases
The mean of the sampling distribution of sample means is _____
equal to the population mean
A method for testing a claim or hypothesis about a parameter in a population, using data measured in a sample, is called ____
hypothesis testing
Based on the effect size conventions, d = 0.90 is a
large effect size
What values are distributed along the x-axis for a sampling distribution of the sample mean?
sample means
The first step to hypothesis testing requires that a researcher ___
state the hypothesis
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 statistics
As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which
the population variance is unknown
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 reports that stress levels among nurses are higher compared to stress levels in the general population, t (20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test?
A two tailed test because the p value is equal to .05
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 test
A point estimate is typically reported with an interval estimate. Why?
all of these
A research design in which different participants are observed one time in each group of a research study is called _
between-subjects design
A researcher conducts two t tests. Test 1 is a one-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a one-tailed test with a larger sample size at a .05 level of significance. What do you know about the critical values for each test?
Test 2 is associated with smaller critical values.
A researcher states that a sample of 100 shoppers spend 112 ± 40 (M ± SEM) dollars on groceries each week. Which value is the standard error of the mean?
40
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 () of 1.6. What is the lower confidence limit for this interval?
8.8
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 () of 4.7. What is the confidence interval at this level of confidence?
80% Cl 15.9, 28.7
State the critical value(s) for a t test using a .05 level of significance in the lower tail only: t(24)
about ~1.711
Computing a one-sample t test is appropriate when ____
all of the above
The probability of committing a Type I error is stated by ______ and the probability for committing a Type II error is stated by ______.
alpha; beta
It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with nonsignificant results?
because it makes little sense to report the size of an effect that you just concluded does not exist
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 equal to at least 12?
equal to the probability of selecting a sample mean that is most equal to 8
Which type of error is used to compute the confidence interval for two independent samples selected from at least one population with an unknown variance?
estimated standard error for the difference
It happens to be the case that the standard error of the sampling distribution of sample means __
is minimal
The criterion for a decision regarding the value stated in a null hypothesis is set by the __
level of significance
Based on the effect size conventions, d = 0.60 is a
medium effect size
Suppose a researcher wants to make sure that the probability of committing a Type I error is less than 5%. How can the researcher control for this?
set the alpha level at .5
Based on the effect size conventions, d = 0.18 is a
small effect size
The less that scores overlap between groups, the ______ the error variance.
smaller
A researcher conducts two t tests. Test 1 is a one-tailed test with a smaller sample size at a .05 level of significance. Test 2 is a one-tailed test with a larger sample size at a .05 level of significance. What do you know about the critical values for each test
test 2 is associated with smaller critical values
A researcher compares differences in mean health scores between students at two local high schools. Assuming that the population variance is unknown, what type of t test is appropriate for this study?
two-independent-sample t test
A researcher reports that stress levels among nurses are higher compared to stress levels in the general population, t(20) = 2.086, p = .05 (d = .12). Was this a one-tailed or a two-tailed test?
two-tailed test because the p value is equal to .05
When a researcher decides to retain the null hypothesis because the rejection region was located in the wrong tail, this is called a ___
type III error
Two researchers (A and B) compute a two-independent-sample t test. For both tests, the standard error is the same, but the mean difference between the groups is larger for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher A
Two researchers (A and B) compute a one-sample t test. For both tests, the standard error is the same, but the mean difference between the sample and value stated in the null hypothesis is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher B
A researcher conducts a study and concludes that a new behavioral health treatment program significantly reduces one's risk for disease compared with risk levels in the general population (d = -0.64). Interpret the size of this effect
Risk levels in the population shifted 0.64 standard deviations below the mean
A researcher conducts two studies. Each study was a one-sample z test. Both studies placed the rejection region in both tails and measured the same sample mean. The beat level in Study 1 was larger than the beta level used in Study 2. Which study is associated with greater power to detect an effect?
Study 1
A local elementary school determined that the average number of volunteers for their "Step into Spring" annual fundraiser has been 14 persons on average (per event). After taking additional measures to recruit volunteers this year, they got 28 people to volunteer. Test whether these additional measures increased the number of volunteers at a .05 level of significance.
There is not enough information to answer this question
The average response time to a bank robbery is about 9 min. A local community wants to improve on this time, so they implement advanced training seminars. They find that the new response time for a sample of 36 police officers is 8 ± 4.2 (M±SD) min. Test whether this advanced training seminar reduced response time at a .05 level of significance.
This advanced training seminar did not reduce response time, t(35) = -1.43, p > .05.
In a sample of 30 participants, a researcher estimates the 95% CI for a sample with a mean of M1 - M2 = 0.7 and an estimated standard error for the difference () of 0.2. What is the confidence interval at this level of confidence?
95% Cl 0.3, 1.1
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 that is at least equal to the population mean?
Both A and B
As a requirement for the t test, researchers compute any type of t test with samples selected from populations in which
The population variance is unknown
A researcher increases the sample size, which will _
decrease the value of standard error
A researcher reports a significant effect with t(14) = 3.24. Compute eta-squared for this result.
n^2= 0.43 (large effect size)
If a researcher obtains a null finding, then what is the decision
they correctly retained the null hypothesis
A type of factor in which different participants are observed in each group, or at each level of the factor, is called
between-subjects factor
A researcher reports that the mean difference in the body weight of rats following a pharmacological versus control treatment is 14 g, with a pooled sample variance equal to 256. What is the effect size for this test using estimated Cohen's d?
d= 0.88; large effect size
______ 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
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 _
estimated to compute a t statistic
A statistical procedure in which a sample statistic is used to estimate the value of an unknown population parameter is called
estimation
Which type of sampling is most often applied by researchers in the behavioral sciences?
experimental sampling
You read about a study testing whether night shift workers sleep the recommended 8 hr per 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
In hypothesis testing, a researcher can never ___
prove his or her hypothesis is correct
Hypothesis testing is called
significance testing
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
A professor finds that the average SAT score among all students attending his college is 1150 150 ( ). He polls his class of 25 students and finds that the average SAT score is 1,200. Suppose he computes a one-sample z test at a .05 level of significance. What is his decision?
to reject the null hypothesis for an upper-tailed test, but to retain the null hypothesis for a two-tailed test
A researcher reports with 90% confidence that 31-37% of Americans believe in ghosts. What is the point estimate for this interval?
34%
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 selects a sample of 9 participants from a population with a mean of 8 and a standard deviation of 3. About 14% of the sample means in this sampling distribution should be between a sample mean of __
9 and 10
In a sample of 14 participants, a researcher estimates the 90% CI for a sample with a mean of M1 - M2 = 10.7 and an estimated standard error for the difference () of 2.9. What is the confidence interval at this level of confidence?
90% Cl 5.5, 15.9
In a sample of 28 participants, a researcher estimates the 95% CI for a sample with a mean of M = 1.5 and an estimated standard error () of 0.3. What is the confidence interval at this level of confidence?
95% CI 0.9, 2.1
A professor teaches a certain section of material using a lot of examples with sports and cars to illustrate. He is concerned that this may have biased his instruction to favor male students. To test this, he measures exam grades from this section of material among women (n = 10) and men (n = 10). The mean score in the male group was 84 ± 4.0 (M ± SD); in the female group, it was 78 ± 8.0 (M ± SD) points. If the null hypothesis is that there is no difference in exam scores, then test the null hypothesis at a .05 level of significance for a two-tailed test.
Exam scores were significantly higher in the male group, t(18) = 2.12, p < .05.
Is a one-sample t test reported differently for one-tailed and two-tailed tests?
No, the same values are reported
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 estimated 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
A researcher has participants rate the likability of a sexually promiscuous person described in a vignette as being male (n = 20) or female (n = 12). The mean likability ratings in each group were 4.0. If the null hypothesis is that there is no difference in likability ratings, then do likability ratings differ at a .05 level of significance?
No, this result is not significant, t(30) = 0
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 test
Suppose you select a sample of three people from a population of four (A, B, C, D). Which of the following samples is possible using the experimental sampling strategy?
Person B, C, and D
A researcher reports a significant mean difference in a given population. If she computes both eta-squared and omega-squared to measure the effect size, then which estimate will be the most conservative?
omega-squared
A researcher conducts a study comparing the obesity rate in a small community to the known obesity rate in the United States. Assuming that the population variance in unknown, what type of t test is appropriate for this study?
one-sample t test
The more that scores in each group ______, the larger the error variance
overlap
What are the two decisions that researchers can make in hypothesis testing
retain or reject the null hypothesis
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 test statistic and finds that the p value for this test is .03. What does this result mean?
there is a 3% likelihood of obtaining the statistics if the null were true
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
Given the following values: = 10, M = 8, = 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
Given the following values: = 6.0, M = 7.6, n = 36, = 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 researcher conducts a study measuring differences in brain activity among rats placed on either a continuous or intermittent reward schedule. Assuming that the population variance in unknown, what t test is appropriate for this study?
two-independent-sample t test
When reporting the results of a one-sample z test using APA format, the ______ does not need to be reported.
critical values
Which of the following explains why point estimation can be a useful procedure to estimate a population mean?
Both b and c
A researcher selects a sample of 32 participants who are assigned to participate in a study with one group. What are the degrees of freedom for this test?
31
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
+/- 2.086
What is the typical level of significance for a hypothesis test in behavioral research?
.05
A researcher selects a sample of 64 participants from a population with a mean of 10 and a variance of 16. What is the standard error of the mean?
0.5
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 () of 1.8. What is the lower confidence limit for this interval?
11.2
A researcher reports that the effectiveness of a new marketing campaign significantly increased sales compared with the previous campaign strategy, t(49) = 2.562, p < .05. Use eta-squared to interpret the effect size for this result
12% of the variability in marketing effectiveness can be accounted for by the new marketing strategy
A researcher selects a sample of 121 participants from a population with a mean of 32 and a standard deviation of 22. What is the standard error of the mean?
2.0
A researcher records the crying time (in minutes) of infants given oral administration of sucrose (n = 12) or tap water (n = 16) prior to a heel prick. The mean crying time in the sucrose group was 3.3 ± 2.4 (M ± SD) min; in the tap water group, it was 7.3 ± 1.6 (M ± SD) min. If the null hypothesis is that there is no difference in crying time, then what is the decision for this test?
Crying time was significantly reduced among infants given the sucrose solution prior to heel prick
Two researchers (A and B) compute a one-sample t test. For both tests, the mean difference between the sample and value stated in the null hypothesis is 5, but the standard error is smaller for Researcher A. Which test is more likely to result in a decision to reject the null hypothesis?
Researcher A
A researcher selects two samples of 64 participants each. In the first sample, the population mean was 10 and the variance was 16. In this 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 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 randomly selects a sample of athletes and reports that their average score on a health and fitness scale is 23. Based on the characteristics of the sample mean, what does this say about the mean in the population?
We expect the population mean to equal 23 because the sample mean is an unbiased estimator of the population mean
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
A researcher reports that the mean difference in response time to an auditory versus a visual cue is 0.83 s, with a pooled sample variance equal to 2.45. What is the effect size for this test using estimated Cohen's d?
d= 0.53; medium effect size
A researcher reports that the mean time it takes to complete an experimental task is 1.4 ± 8.0 (M ± SD) s. If the null hypothesis was that the mean equals 1.0, then what is the effect size for this test using estimated Cohen's d?
d=.05, small effect size.
Which of the following is an assumption for computing any type of independent sample t test?
all of these
A researcher randomly selects a sample of participants from a population with a variance of 4. If a researcher selects a sample of 16 participants with a mean of 12, then what is the mean and standard error for the sampling distribution of the mean?
mean= 12, standard error= 0.5
A researcher reports that college students consume an average of 3.6 alcoholic drinks per week. What is the interval estimate in this example?
interval estimate is not given
researcher obtains z = 1.80 for a one-sample z test. What is the decision for this test at a .05 level of significance?
it depends on whether the test in one tailed or two tailed
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 0.3
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
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d?
mean scores shifted 0.88 standard deviations in the population
State the critical value(s) for a t test using a two-tailed test at a .05 level of significance: t(20).
+/- 2.093
A researcher reports the following result for a one-sample z test at a .05 level of significance: z = 1.88, p = -.06 (d = .25). Is this result significant?
No, the decision is to retain the null hypothesis
A researcher reports that the standard deviation in Population A is = 2.3 and the standard deviation in Population B is = 4.3. Which population is associated with the highest power to detect an effect?
Population A
A researcher reports that the size of an effect in Population A is d = 0.10 and the effect size in Population B is d = 0.34. Which population is associated with greater power to detect an effect
Population B
A researcher selects a sample of 36 students from a school population with a mean IQ of 100 and standard deviation of 12. She determines that the mean IQ in this sample is 104. Assuming she computes a one-sample z test at a .05 level of significance, what is the decision for a two-tailed test?
Reject the null hypothesis; IQ scores in this sample are significantly higher than those in the copulation
Two researchers select a sample for a population with a mean of 12.4 and a standard deviation of 9. Researcher A selects a sample of 30 participants. Researcher B selects a sample of 40 participants. Which sample is associated with a smaller standard error?
Researcher B, because the sample size was larger
A researcher computes a one-sample z test in two studies. Both studies used the same alpha level, placed the rejection region in both tails, and measured the same sample mean. The researcher selects a sample of 30 participants in Study 1 and decides to retain the null hypothesis. She selects a sample of 60 participants in Study 2 and decides to reject the null hypothesis. Which of the following is the best explanation for why the decision was different in Study 1 and Study 2?
The different decisions in Study 1 and Study 2 are possible because the second test was associated with greater power to detect an effect.
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 25, = 5, = 7Researcher B: n = 25, = 32, = 7
They both have the same standard error
The estimated standard error in the t statistic uses the ______ to estimate the _
sample variance, population variance
A distribution of all sample means or sample variances that could be obtained in samples of a given size from the same population is called ______.
a sampling distribution
In terms of characterizing samples, statistical theory was developed using a sampling strategy in which __
all of these
Researchers state a level of significance in terms of an alpha level. The alpha level indicates
all of these
What values are distributed along the x-axis for a sampling distribution of the sample variance?
sample varience
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 theorum
Which of the following is not one of the four steps to hypothesis testing?
identify hypothetical data
A researcher selects two samples of 25 participants each. In the first sample, the population mean was 32 and the variance was 8. In this second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean?
none, both samples will have the same value for standard error
Which of the following statements regarding the null hypothesis is true?
null hypothesis always makes statements about a population perameter
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 36, = 12, = 9Researcher B: n = 36, = 12, = 6
researcher B
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
A researcher selects from a participant pool of four males and six females. He determines that the probability of selecting two female participants is p = .30. Based on this probability, what strategy did the researcher use to sample participants?
sampling without replacement
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 hypothesisstated by an alpha level
The mean crying time of infants during naptime at a local preschool is 12 min. The school implements a new naptime routine in a sample of 25 infants and records an average crying time of 8 ± 4.6 (M±SD) min. Test whether this new naptime routine reduced crying time at a .05 level of significance.
the new naptime routine significantly reduced crying time. t(24)=-4.35, p < .05
The following samples were selected by two researchers. Which is associated with a smaller standard error of the mean?Researcher A: n = 18, = 8, = 2.4Researcher B: n = 12, = 8, = 2.4
they both have the same standard error
A researcher obtains z = 1.45 for a one-sample z test. What is the decision for this test at a .05 level of significance?
to retain the null hypothesis
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 ____
u= 78
How is the standard error of the mean typically reported in a graph
using error bars
