Research Methods exam 2

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the decision?

. Reject H0: zobt is located beyond zcrit, and p < α

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the conclusion

. The cognitive therapy is effective: students should go through the therapy to improve their IQ scores.

The criteria for a decision regarding the value stated in a null hypothesis is set by the

. level of significance

The estimated standard error in the t statistic uses the ________ to estimate the ________ when the population variance is unknown.

. sample variance; population variance

With α = .05, what is the critical t value for a one-tailed test with n = 15?​

. t = 1.761

What is the typical level of significance for a hypothesis test in behavioral research, including psychology?

.05

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the p value? Enter the numerical value below. Include four digits after the decimal point.

0.0456

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), calculate the effect size using Cohen's d. Enter the numerical value below. Include two digits after the decimal point.

0.33

A psychologist administered a cognitive development test to a group of 9 children from a small local elementary school who went through a special training. The mean score for this group of children was 5 with a standard deviation of 2.61. She finds in a research article that the overall mean score for children in elementary school is 3.8 but the article did not provide the standard deviation. Assuming she computes a two-tailed t statistic at a .05 level of significance (α), what is the value of the estimated standard error of the mean? Enter the numerical value below. Include two digit after the decimal point.

0.87

A psychologist administered a cognitive development test to a group of 9 children from a small local elementary school who went through a special training. The mean score for this group of children was 5 with a standard deviation of 2.61. She finds in a research article that the overall mean score for children in elementary school is 3.8 but the article did not provide the standard deviation. Assuming she computes a two-tailed t statistic at a .05 level of significance (α), what is the value of the t statistic (tobt)? Enter the numerical value below. Include two digits after the decimal point.

1.38

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the value of the positive zcrit (critical region). Enter the numerical value below. Include two digits after the decimal point.

1.96

A doctor randomly selects two groups of patients with a medical condition. Group 1 received drug A and Group 2 received drug B. He does some preliminary processing of the data and get the table with the information shown here. The doctor wants to know if there is a significant difference between the two groups. Assuming he computes a two-tailed two-independent samples t statistic at a .05 level of significance (α), what is the estimated error of the difference? Enter the numerical value below. Include one digit after the decimal point. n1=16, n2=16 m1=72 m2=58 s2/1=28 s2/2=36

2

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the value of the standard error of the mean? Enter the numerical value below. Include one digit after the decimal point.

2

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the value of the z statistic (zobt). Enter the numerical value below. Include two digits after the decimal point.

2

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 of the sample mean?

2

A doctor randomly selects two groups of patients with a medical condition. Group 1 received drug A and Group 2 received drug B. He does some preliminary processing of the data and get the table with the information shown here. The doctor wants to know if there is a significant difference between the two groups. Assuming he computes a two-tailed two-independent samples t statistic at a .05 level of significance (α), what is the value of the positive tcrit (critical region)? Enter the numerical value below. Include three digits after the decimal point. n1=16, n2=16 m1=72 m2=58 s2/1=28 s2/2=36

2.042

A psychologist administered a cognitive development test to a group of 9 children from a small local elementary school who went through a special training. The mean score for this group of children was 5 with a standard deviation of 2.61. She finds in a research article that the overall mean score for children in elementary school is 3.8 but the article did not provide the standard deviation. Assuming she computes a two-tailed t statistic at a .05 level of significance (α), what is the value of the positive tcrit (critical region)? Enter the numerical value below. Include three digits after the decimal point.

2.306

A researcher selects a sample of 32 participants who are assigned to participate in a study with one group that is going to be compared to a population with an unknown variance. What are the degrees of freedom for this test?

31

A doctor randomly selects two groups of patients with a medical condition. Group 1 received drug A and Group 2 received drug B. He does some preliminary processing of the data and get the table with the information shown here. The doctor wants to know if there is a significant difference between the two groups. Assuming he computes a two-tailed two-independent samples t statistic at a .05 level of significance (α), what is the average (pooled) variance? Enter the numerical value below. Include one digit after the decimal point. n1=16, n2=16 m1=72 m2=58 s2/1=28 s2/2=36

32

A doctor randomly selects two groups of patients with a medical condition. Group 1 received drug A and Group 2 received drug B. He does some preliminary processing of the data and get the table with the information shown here. The doctor wants to know if there is a significant difference between the two groups. Assuming he computes a two-tailed two-independent samples t statistic at a .05 level of significance (α), what is the value of the statistic (tobt)? Enter the numerical value below. Include one digit after the decimal point. n1=16, n2=16 m1=72 m2=58 s2/1=28 s2/2=36

7

What is measured by the denominator of the z statistic?​

A likely distance between M and µ that would be expected if H0 was true

A psychologist administered a cognitive development test to a group of 9 children from a small local elementary school who went through a special training. The mean score for this group of children was 5 with a standard deviation of 2.61. She finds in a research article that the overall mean score for children in elementary school is 3.8 but the article did not provide the standard deviation. Assuming she computes a two-tailed t statistic at a .05 level of significance (α), what is the decision?

Accept H0: tobt is located before tcrit

It is most appropriate to report effect size with a significant result. Why is it generally inappropriate to report effect size with insignificant results?

Because it makes little sense to report the size of an effect for which you couldn't find evidence.

What is the consequence of a Type II error?​

Concluding that a treatment has no effect when it really does

A researcher is testing a new cognitive therapy that is supposed to improve IQ scores. She selects a sample of 36 students to undergo therapy and then take an IQ test. The sample of students came 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 two-tailed z test at a .05 level of significance (α), what is the null and the alternative hypothesis?

H0: μ = 100 (the cognitive therapy does not affect IQ); H1: μ ≠ 100 (the cognitive therapy affects IQ)

A psychologist administered a cognitive development test to a group of 9 children from a small local elementary school who went through a special training. The mean score for this group of children was 5 with a standard deviation of 2.61. She finds in a research article that the overall mean score for children in elementary school is 3.8 but the article did not provide the standard deviation. Assuming she computes a two-tailed t statistic at a .05 level of significance (α), what is the null and the alternative hypothesis?

H0: μ = 3.87 (the special training does not affect test score); H1: μ ≠ 3.87 (the special training affects test score)

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.

A research article reports the following result for a one-sample t statistic at a .05 level of significance: t = 1.88, p = .07 ( d = .25). Is this result significant?

No, it is not significant; the decision is to accept the null hypothesis because p > α

A researcher reports the following result for a one-sample z test at a .05 level of significance (α): z = 1.88, p = .06 ( d = .25). Is this result significant?

No, the decision is to accept the null hypothesis because p > α

A doctor randomly selects two groups of patients with a medical condition. Group 1 received drug A and Group 2 received drug B. He does some preliminary processing of the data and get the table with the information shown here. The doctor wants to know if there is a significant difference between the two groups. Assuming he computes a two-tailed two-independent samples t statistic at a .05 level of significance (α), what is the decision?

Reject H0: tobt is located beyond tcrit

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.

What is measured by the numerator of the z statistic? ​

The actual distance between M and µ

A professor finds out that mean score of all the students that has taken his class is 78%. She is now going to give the exam to her new group of students but before the exam she is going to ask the students to take a deep breath and to relax to test whether or not scores change. In this example, the null hypothesis is

The new group of students will also score 78%.

The power in hypothesis testing is

The probability of rejecting a false null hypothesis

Maddie conducts two different one independent sample t statistics. The first statistic Maddie conducts is a two-tailed test with a sample size of 5 at a .05 level of significance. The second test is a two-tailed test with a sample size of 50 also at a .05 level of significance. What can you say about the degrees of freedom of these statistics?

The second statistic Maddie conducted has a larger number of degrees of freedom than the first statistic because the first statistic had df = 4 and the second had df = 49.

Which of the following is a fundamental difference between the t statistic and a z-score? ​

The t statistic uses the sample variance in place of the population variance.

A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the null hypothesis (H0) say about the treatment?​

The treatment has no effect on the scores.

What are the two decisions that researchers can make in hypothesis testing?

accept or reject the null hypothesis

Researchers state a level of significance in terms of an alpha level. The alpha level indicates

all of the above

Computing a one-sample t test is appropriate when

all of these are appropriate

The probability of committing a Type I error is stated by ________; the probability for committing a Type II error is stated by ________.

alpha; beta

The one-sample z test is a hypothesis test used to test hypotheses

concerning a single population with a known variance

When reporting the results of your test statistics using APA (American Psychological Association) format, the ________ does not need to be reported.

critical values

A researcher reports that the mean ratings of liking of a restaurant on campus from the new freshmen students is 2.8 with a standard deviation of 2.4. If the mean rating of liking of all the college students on campus is 1.6, then what is the effect size for this test using estimated Cohen's d?

d = 0.50; medium effect size

Computing a two-independent sample t statistic is appropriate when

different participants are assigned to each group and only observed once, two populations or groups need to be compared, and the population variance is unknown

________ 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 ________ to compute a t statistic.

estimated

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 = 0.99 is a

large effect size

An undergraduate student at SUNY Oneonta wants to determine whether the number of hours night shift workers sleep is similar to the recommended 8 hours per day that the general population usually spends sleeping at night. Assuming that the population variance of sleep hours (per day) is unknown, what type of statistic is appropriate for this study?

one-sample t statistic

If the value of the test statistic is in the rejection region, then

p<0.05

In hypothesis testing, a researcher can never

prove that his or her hypothesis is correct

Which of the following is an accurate definition of a Type I error?

rejecting a true null hypothesis

The first step to hypothesis testing requires that a researcher

state the 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 type of t statistic is appropriate to compare these groups?

two-independent sample t statistic

​ A researcher selects a sample and administers a treatment to the individuals in the sample. If the sample is used for a hypothesis test, what does the alternative hypothesis ( H 1 ) say about the treatment?

​The treatment causes a change in the scores.

A sample of n = 16 scores has a mean of M = 65 and an estimated standard error (sM ) of 2 points. What is the sample variance?

​s2 = 64