1) Mark is interested in studying whether eating chocolate before a test will make a person get a higher score on the test. He talks to half of his classmates before the exam, and they agree to eat a piece of chocolate before taking the exam. The other half of the class gets no chocolate before taking the exam.
a. Identify the independent variable in this experiment. Describe whether this variable is a categorical, ordinal, interval, or ratio variable.
b. Identify the dependent variable in this experiment. Describe whether this variable is a categorical, ordinal, interval, or ratio variable.
c. What is the null hypothesis for this experiment? Use the specific terms from this experiment (group names and what is measured) to describe the null hypothesis.
d. What is the alternative hypothesis for this experiment? Use the specific terms from this experiment (group names and what is measured) to describe the alternative hypothesis.
2) Using the research design in #1, Mark conducts a statistical test to compare these two groups to each other. He gets a p-value of 0.042.
a. Should mark reject or accept the null hypothesis based on this p-value?
b. Based on your decision, what does this mean about the difference between the two groups?
c. In terms of probability, what does the value p = 0.07 mean (in your own words)?
d. Suppose Mark got a p –value of 0.32 instead. Should mark accept or reject his null hypothesis based on this p-value? If so, what would this decision mean about the difference between the two groups (in your own words)?
3) Sonya works in a lab that develops new medication for a pharmaceutical company. She is conducting research to see if the effects of the anti-depressant medication Prozac help to lower depression in patients compared to the anti-depressant Zoloft. She gives Prozac to twenty volunteers and collects their rating of depression on a Likert scale from 1-10 (1 = lowest depression level, 10 = highest possible depression). She then gives Zoloft to twenty other volunteers and collects the same rating of depression from each volunteer.
a. Identify the independent variable in this experiment. Describe whether this variable is a categorical, ordinal, interval, or ratio variable.
b. Identify the dependent variable in this experiment. Describe whether this variable is a categorical, ordinal, interval, or ratio variable.
c. What is the null hypothesis for this experiment? Use the specific terms from this experiment (group names and what is measured) to describe the null hypothesis.
d. What is the alternative hypothesis for this experiment? Use the specific terms from this experiment (group names and what is measured) to describe the null hypothesis.
4) Based on the experiment described in #3, the average rating of depression was 5.9 for people taking Prozac and 7.3 for people taking Zoloft.
a. Even though there is a difference in depression rating between the Zoloft and Prozac samples, explain in your own words why this is not enough to reject or accept the null hypothesis.
b. Suppose Sonya runs an appropriate statistical test to compare these two group means. She gets a p-value equal to 0.50. What does this p-value mean (as a probability/percent)?
c. Based on this p-value, are the two groups significantly different from each other or the same?
5) Briefly describe a research study that you might be interested in doing that compares two groups together.
6) Based on your study in #5:
a. What is the name of your independent variable?
b. Is the independent variable categorical, ordinal, interval, or ratio?
c. What are the names of the two different groups (i.e. blue pill rats vs. control rats)?
d. What is the name of your dependent variable?
e. Is the dependent variable categorical, ordinal, interval, or ratio?
f. How is the dependent variable measured?
g. What do you think the results might be (reject the null hypothesis or accept the null hypothesis)?
7) Calculate a 80% confidence interval using the information below. Follow the 4 steps outlined in lecture to find the two scores that make up the 80% confidence interval. Show work
a. σ = 14 μ = 55 N = 10
b. σ = 14 μ = 55 N = 1008) Calculate a 90% confidence interval using the information below. Follow the 4 steps outlined in lecture to find the two scores that make up the 90% confidence interval. Show work
a. σ = 14 μ = 55 N = 10
b. σ = 14 μ = 55 N = 1009) Calculate a 98% confidence interval using the information below. Follow the 4 steps outlined in lecture to find the two scores that make up the 98% confidence interval. Show work
σ = 10 μ = 100 N = 20010) Choose the correct words to complete this sentence:
(Hint: Your work in #7, #8, and #9 might help you here.)
You can see that when the total number of people (N) in a sample _________, a confidence interval will ________. This is because larger samples are closer to the actual size of the overall population and confidence intervals become more precise. a. increases; increases
b. increases; decreases
c. stays the same; increase
d. decreases; decreases
11) In your own words, what does a confidence interval measure? Explain this concept as if you were speaking to someone with no background in statistics.
IN SPSS
Note: If you do not have the SPSS program installed on your computer or you cannot access the program online, please visit the course Canvas page and open the document called “Instructions for Accessing Excel and SPSS from your Home” at the top. If you continue to experience difficulties, email me ASAP so you can get the program running to complete this lab assignment.
A. Open up the file “Lab 4 Input – PSY320” in SPSS on your computer.
***You CANNOT just click on it and open this file ***
1) You need to go to http://www.csun.edu/it/mycsunsoftware-0 and run SPSS.
2) Then download the data file for this lab assignment from CANVAS
3) In SPSS, go to File>>Open >> Data and click on the file you downloaded.
4) You may have to search for it on your computer (usually it is in the “Downloads” folder).
B. Follow the instructions given in lab or on the instructional video to complete the SPSS portion of this homework. COPY AND PASTE YOUR FINAL WORK HERE.