SOCI 332 WEEKLY ASSIGNMENT 5
For the following question(s): A school counselor tests the level of depression in fourth graders in a particular class of 20 students. The counselor wants to know whether the kind of students in this class differs from that of fourth graders in general at her school. On the test, a score of 10 indicates severe depression, while a score of 0 indicates no depression. From reports, she is able to find out about past testing. Fourth graders at her school usually score 5 on the scale, but the variation is not known. Her sample of 20 fifth graders has a mean depression score of 4.4. Use the .01 level of significance.
1. The counselor calculates the unbiased estimate of the population’s variance to be 15. What is the variance of the distribution of means?
A) 15/20 = 0.75
B) 15/19 = 0.79
C) 152/20 = 11.25
D) 152/19 = 11.84
2. Suppose the counselor tested the null hypothesis that fourth graders in this class were less depressed than those at the school generally. She figures her t score to be-.20. What decision should she make regarding the null hypothesis?
A) Reject it
B) Fail to reject it
C) Postpone any decisions until a more conclusive study could be conducted
D) There is not enough information given to make a decision
3. Suppose the standard deviation she figures (the square root of the unbiased estimate of the population variance) is .85. What is the effect size?
A) 5/.85 = 5.88
B) .85/5 = .17
C) (5- 4.4)/.85 = .71
D) .85/(5- 4.4) = 1.42
For the following question(s): Professor Juarez thinks the students in her statistics class this term are more creative than most students at this university. A previous study found that students at this university had a mean score of 35 on a standard creativity test. Professor Juarez finds that her class scores an average of 40 on this scale, with an estimated population standard deviation of 7. The standard deviation of the distribution of means comes out to 1.63.
4. What is the t score?
A) (40- 35)/7 = .71
B) (40- 35)/1.63 = 3.07
C) (40- 35)/72= 5/49 = .10
D) (40- 35)/1.632= 5/2.66 = 1.88
5. What effect size did Professor Juarez find?
A) (40- 35)/7 = .71
B) (40- 35)/1.63 = 3.07
C) (40- 35)/72= 5/49 = .10
D) (40- 35)/1.632= 5/2.66 = 1.88
6. If Professor Juarez had 30 students in her class, and she wanted to test her hypothesis using the 5% level of significance, what cutoff t score would she use? (You should be able to figure this out without a table because only one answer is in the correct region.)
A) 304.11
B) 1.699
C) -.113
D) -2.500
SPSS ASSIGNMENT (10 Points)
Single Sample & Dependent Samples t Tests
Review the five steps of hypothesis testing and complete the following problem.Choose one of the problems to solve belowand follow the given instructions. Be sure to cut and past the appropriate result boxes from SPSS under each problem. All calculations should be coming from SPSS.
t Test for a Single Sample:
Open SPSS
Enter the number of activities of daily living performed by the depressed clients studied in #1 in the Data View window.
In the Variable View window, change the variable name to “ADL” and set the decimals to zero.
Click Analyzeà Compare Meansà One-Sample T testà the arrow to move “ADL” to the Variable(s) window.
Enter the population mean (14) in the “Test Value” box.
Click OK.
1. Researches are interested in whether depressed people undergoing group therapy will perform a different number of activities of daily living after group therapy. The researchers have randomly selected 12 depressed clients to undergo a 6-week group therapy program.
Use the five steps of hypothesis testing to determine whether the average number of activities of daily living (shown below) obtained after therapy is significantly different from a mean number of activities of 14 that is typical for depressed people. (Clearly indicate each step).
Test the difference at the .05 level of significance and, for practice, at the .01 level (in SPSS this means you change the “confidence level” from 95% to 99%).
In Step 2, show all calculations.
As part of Step 5, indicate whether the behavioral scientists should recommend group therapy for all depressed people based on evaluation of the null hypothesis at both levels of significance and calculate the effect size.
|
CLIENT |
AFTER THERAPY |
|
A |
17 |
|
B |
15 |
|
C |
12 |
|
D |
21 |
|
E |
16 |
|
F |
18 |
|
G |
17 |
|
H |
14 |
|
I |
13 |
|
J |
15 |
|
K |
12 |
|
L |
19 |
t Test for Dependent Means:
Open SPSS
Enter the number of activities of daily living performed by the depressed clients studied in Problem 2 in the Data View window. Be sure to enter the “before therapy” scores in the first column and the “after therapy” scores in the second column.
In the Variable View window, change the variable name for the first variable to “ADLPRE” and the variable name for the second variable to “ADLPOST”. Set the decimals for both variables to zero.
Click Analyzeà Compare MeansàPaired-Samples T Testàthe arrow to move “ADLPRE” to the Paired Variable(s) windowà “ADLPOST” and then click the arrow to move the variable to the Paired Variable(s) window.
Click OK.
2. Researchers are interested in whether depressed people undergoing group therapy will perform a different number of activities of daily living before and after group therapy. The researchers have randomly selected 8 depressed clients in a 6-week group therapy program.
Use the five steps of hypothesis testing to determine whether the observed differences in numbers of activities of daily living (shown below) obtained before and after therapy are statistically significant at the .05 level of significance and, for practice, at the .01 level. (Clearly indicate each step).
In Step 2, show all calculations. As part of Step 5, indicate whether the researchers should recommend group therapy for all depressed people based on evaluation of the null hypothesis at both levels of significance and calculate the effect size.
|
CLIENT |
BEFORE THERAPY |
AFTER THERAPY |
|
A |
12 |
17 |
|
B |
7 |
15 |
|
C |
10 |
12 |
|
D |
13 |
21 |
|
E |
9 |
16 |
|
F |
8 |
18 |
|
G |
14 |
17 |
|
H |
11 |
8 |
DISCUSSION QUESTION
Last week we talk about the uses of a crosstabulation and the benefits of creating this “snapshot” of your data. Create a crosstab for your data and include in the post. Briefly explain. Based on the variables that you have chosen for your research, what test statistic are you planning to use and why is this the best fit? Be sure to explain your answers.
SOC 332 Quiz 5
Question 1 of 25 0.8 Points
Effect size is a measure of:
A.the difference between individual members of a sample
B.the extent to which two populations overlap
C.the extent to which two populations do not overlap
D.the statistical significance of a research study
Question 2 of 25 0.8 Points
Which of the following is NOT a correct statement about effect size of a study finding:
A.It provides much information about statistical significance.
B.It is a standardized measure of lack of overlap between populations.
C.It increases with greater differences between means.
D.It can be converted to a standardized effect size.
Question 3 of 25 0.8 Points
According to Cohen’s conventions, for research that compares means, a large effect size in which only about 53% of the populations of individuals overlap would be:
A..5
B..6
C..7
D..8
Question 4 of 25 0.8 Points
Some IQ tests have a standard deviation of 16 points. If an experimental procedure produced an increase of 3.2 IQ points, the effect size would represent a __________ effect size.
A.small
B.medium
C.large
D.extra large
Question 5 of 25 0.8 Points
A standard verbal memory test is known to have a standard deviation of 10 points. If an experimental procedure produced an increase of 8 points, the effect size would represent a __________ effect size.
A.small
B.medium
C.large
D.unable to determine without additional information
Question 6 of 25 0.8 Points
In what way is effect size most comparable to a Z score?
A.It can range from ?1 to +1
B.It provides a direct indication of statistical significance
C.It provides a standard for comparison for results across studies, even studies using different measures
D.All of the above
Question 7 of 25 0.8 Points
Cohen has proposed some effect-size conventions based on the effects observed in psychology research in general because:
A.researchers frequently need to decide whether the effect size that they have found allows them to reject the null hypothesis
B.it is usually difficult to know how big an effect to expect from a given experiment
C.Cohen originally developed the relevant scales
D.they are more accurate than figuring a minimum meaningful difference
Question 8 of 25 0.8 Points
The effect size conventions proposed by Cohen are useful to researchers for:
A.predicting the value of the measured variable to use for the experimental condition
B.evaluating research results to determine if they are statistically significant
C.predicting the effect of a study on various populations
D.determining the power of a planned study
Question 9 of 25 0.8 Points
A statistical method for combining effect sizes from different studies is known as:
A.combination analysis
B.comparison analysis
C.multivariate analysis
D.meta-analysis
Question 10 of 25 0.8 Points
Reviews of a collection of studies on a particular topic that use meta-analyses represent an alternative to traditional __________ articles. These traditional articles describe and evaluate each study and then attempt to draw some overall conclusion.
A.general educational method
B.computer-assisted research
C.engagement goal setting
D.narrative literature review
Question 11 of 25 0.8 Points
It is useful to understand statistical power for which of the following reasons?
A.Determining the number of participants to use in an experiment
B.Making sense of findings in research articles
C.Understanding the implications of a study that is not statistically significant
D.All of the above
Question 12 of 25 0.8 Points
If statistical power for a given research study is .40, one can say that: “Assuming the researcher’s prediction is correct, the researcher has a __________ chance of attaining statistically significant results.”
A.20%
B.40%
C.45%
D.80%
Reset Selection
Question 13 of 25 0.8 Points
When a study has only a small chance of being significant even if the research hypothesis is true, the study is said to have:
A.low power
B.low probability
C.low market value
D.low sample size
Question 14 of 25 0.8 Points
Standard power tables are useful for:
A.directly determining the power of an experiment
B.determining the predicted score (but not the variance) for the group exposed to the experimental manipulation
C.determining the predicted effect size of a proposed experiment
D.determining the probability of falsely accepting the research hypothesis
Question 15 of 25 0.8 Points
Effect size is one of the two major factors that contribute to power. Another factor is:
A.the sample’s standard deviation
B.the minimum meaningful difference
C.the sample size
D.the mean of the known population
Question 16 of 25 0.8 Points
A researcher may not be able to change the effect size of a planned study to increase power. Another aspect of a planned study that the researcher can usually change to increase power is:
A.the sample size
B.the beta level
C.the population parameters
D.the sample mean
Question 17 of 25 0.8 Points
In actual practice, the usual reason for determining power before conducting a study is to:
A.eliminate the possibility that a mistake may occur
B.ensure that regardless of whether the research hypothesis is true, the experiment will yield a significant result
C.determine the number of participants needed to have a reasonable chance of getting a significant result if the research hypothesis is true
D.recognize the likelihood that the experiment will need to be repeated
Question 18 of 25 0.8 Points
What effect will using a one-tailed test over a two-tailed test have on power (presuming the true population difference is in the expected direction)?
A.it will increase power
B.it will have no effect on power
C.it will decrease power
D.power cannot be calculated if a one-tailed test is used
Question 19 of 25 0.8 Points
Using a two-tailed test makes it __________ to get significance on any one tail. Thus, keeping everything else the same, power __________ with a two-tailed test than with a one-tailed test.
A.easier; more
B.harder; less
C.easier; less
D.harder; more
Question 20 of 25 0.8 Points
If the research hypothesis is true, but the study has a low level of power:
A.there is a high probability that the study will have a significant result
B.the probability of getting a significant result is low
C.the null hypothesis will almost certainly be rejected
D.the significance level selected is probably too lenient (for example, .10 instead of .05)
Question 21 of 25 0.8 Points
Practical significance is a combination of statistical significance and:
A.effect size
B.the level of measurement (whether it is equal interval or ordinal)
C.the population parameters
D.the amount over or under that level that the sample scored
Question 22 of 25 0.8 Points
In statistics, we cannot state that the research hypothesis is ever definitely false. However, if one fails to reject the null hypothesis in a study with a high level of power, this allows us to:
A.suspect that the research hypothesis may still be true
B.conclude that the research hypothesis is most likely false
C.make no statements about the research hypothesis
D.reject the notion that the effect size has anything to do with statistical significance
Question 23 of 25 0.8 Points
What is the most likely explanation for why a study with a very small effect size came out significant?
A.the study had a large sample size
B.the study had a large population standard deviation
C.the researcher used an insensitive hypothesis-testing procedure
D.the researcher used a two-tailed test
Question 24 of 25 0.8 Points
When judging a study’s results, there are two important questions. They are:
A.How large is the power and how competent are the researchers?
B.How stringent is the significance level and how small is the effect size?
C.Is the result statistically significant and is the effect size large enough for the results to be meaningful?
D.Is the study replicable and can we draw conclusions despite not having attained statistical significance?
Question 25 of 25 0.8 Points
If the results of a study are not statistically significant and the sample size is large, then:
A.the result is very important
B.the result proves the null hypothesis
C.the research hypothesis is probably false
D.the result proves the research hypothesis
