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Psyc 011 Midterm 1

Dr. Michael A. Erickson

26 January 2022

Instructions

I had hoped that I would be able to make this exam a quiz on Canvas,

but with all of the mathematical notation and tables, it ended up being

more than I felt confident presenting to the class. I made a lot of

progress, though, so hopefully next time!

1. Write your answers on separate pieces of paper along with your

work. You will scan these pages and turn them in at the end of the

exam.

2. The exam is open book and open notes. You may use a calculator.

3. Because of this, you must show all of your work on paper (or in a

spreadsheet program if you wish), and you must submit a .pdf of

your work and answers along with the exam.

4. Your writing must be clear. If your TA cannot read your writing

on an item, you will not receive credit.

5. The exam will take place during the normal class time.

6. The exam will be proctored on Zoom. Use the regular class link.

You must remain on Zoom with your camera on until you turn the

exam in. You must DM your TA when you are done with the exam

before you leave Zoom.

7. People with SDRC accommodation letters indicating the need for

extra time will an extended deadline. Direct message Dr. Erickson

and your TA to make sure that this is set up properly for you.

Questions

1. Identify the following statements as descriptive or inferential and

justify your response.

a. Based on the opinions of my one of my classes, UCR students

are evenly split between wanting to do online vs. face-to-face

classes

b. The Department of Agriculture anticipated an increase of 8% in

orange production this year.

c. On the basis of a sample of 1,000 respondents, it appears that

56% of the population opposes providing aid to foreign nations.

d. Results of a study suggest that women are more empathetic

than men.

e. As of the first day of class this quarter, the Department of Psy-

chology had 2,112 majors.

psyc 011 midterm 1 2

f. The average teaching load for faculty in the Department of Psy-

chology is 5 1/3 units per quarter.

g. A poll of 800 likely voters predicted Mayor Patricia Lock Daw-

son would earn 58% of the votes if she runs for Mayor of River-

side again.

2. Explain the difference between statistics and parameters.

3. Which scale of measurement is being described? “8 means simply

more than 6; the difference between 8 and 6 may not be same as

the difference between 4 and 2”

a. nominal

b. ordinal

c. interval

d. ratio

4. What level of measurement is used when students are asked their

major, and the count for each major is displayed?

a. nominal

b. ordinal

c. ratio

d. interval

5. Arrange the following scores into a simple frequency distribution.

Construct a histogram. Describe the shape of the distribution. Here

are the scores:

21, 18, 19, 21, 21, 19, 18, 18, 22, 21, 19, 19, 19, 18, 22, 21, 18, 20,

24, 18, 19, 19, 16, 20, 17

6. When you compute a mean, how do you know whether you are

computing the parameter µ or the statistic X?

7. If a distribution has a mean X = 30 and its median = 25, is it

likely to be positively skewed, negatively skewed, or symmetrical?

8. Find the mean, median, and mode for the sample frequency distri-

bution.

X f

35 1

34 3

33 2

32 2

31 1

30 3

psyc 011 midterm 1 3

X f

29 4

27 1

26 2

24 1

23 1

9. Explain the differences between the standard deviation of a popula-

tion, the standard deviation of a sample used to estimate a popula-

tion standard deviation, and the standard deviation used to describe

a sample. Which symbol matches each kind of standard deviation

(S, σ, ŝ)?

10. For the following distribution, compute the standard deviation S.

10, 24, 25, 19

11. The following scores were taken from a larger distribution with

X = 50, and S = 10. Compute the z score for each score.

67, 50, 40, 42

12. Construct a boxplot for a distribution with the following char-

acteristics: mean = 12; median = 17; 25th percentile = 10; 75th

percentile = 18; lowest score = 7; highest score = 23. Describe

the form of the distribution. What would be the lower and upper

boundaries for outliers?

13. Calculate an effect size index (d) and give a verbal description.

X1 = 50 X2 = 65 σ = 30

14. Compute the correlation coefficient r and the coefficient of deter-

mination for the following data. Most of the information you need

to carry out this computation is included in the tables below.

i Xi Yi

1 23 47

2 29 60

3 31 10

4 36 22

5 47 29

psyc 011 midterm 1 4

1 These questions are extra credit,

so do not worry if you do not wish to

answer either or both of them.

i Xi X Xi − X

(

Xi − X

)2

1 23 33.2 -10.2 104.04

2 29 33.2 -4.2 17.64

3 31 33.2 -2.2 4.84

4 36 33.2 2.8 7.84

5 47 33.2 13.8 190.44

i Yi Y Yi − Y

(

Yi − Y

)2

1 47 33.6 13.4 179.56

2 60 33.6 26.4 696.96

3 10 33.6 -23.6 556.96

4 22 33.6 -11.6 134.56

5 29 33.6 -4.6 21.16

15. Using the information from the previous question, plot a scatter-

plot showing each datapoint.

16. Which correlation coefficient r shows the strongest correlation?

a. r = −.63

b. r = .56

c. r = 1.12

d. r = .14

17. Which correlation coefficient r shows the weakest correlation?

a. r = −.78

b. r = .66

c. r = .24

d. r = .38

Extra Credit

1. Using the data from the previous question on correlation, compute

a and b for the regression equation Ŷ = a + b X.1

2. Using the information from the previous questions, add the proper

regression line to the scatterplot above.

- Instructions
- Questions