Psych 209/Kerr/Autumn 2010
1
Descriptive Statistics/Excel Assignment 2 (15 pt)
The purpose of this assignment is to give you practice making scatterplots, both by hand and using
Excel, as well as calculating and interpreting the Pearson Product Moment correlation coefficient.
DUE DATE: At the beginning of lecture Monday, November 1st. Late assignments will be
accepted with the loss of 3 points during sections on Tuesday, November 2nd. Late assignments
will be accepted with the loss of 5 points at the beginning of lecture on Wednesday, November 3rd.
Assignments will not be accepted after Wednesday, November 3rd.
Background reading: (1) Goodwin Chapter 9 and (2) information provided during lab on Thursday
October 21nd.
See the webpage below for help understanding the way scatterplots “map” to the Pearson Product
Moment correlation coefficient, and the influence of number of participants. Use the New Sample
button to see different examples.
http://thesaurus.maths.org/mmkb/entry.html?action=entryByConcept&id=450&langcode=en&expand=0
Data for the assignment:
The data for Part 1 and Part 2 are in the table below.
The data for Part 3 are in an Excel file on the class website. See Part 3 for information on how to
download the file.
ID
SchHrs
Money
Education
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
25
27
45
30
26
20
20
35
32
20
20
15
25
14
30
6
4
4
5
6
3
7
5
5
6
6
6
2
5
4
7
7
7
6
7
6
7
7
6
7
4
7
7
7
7
Note:
These data were sampled from the class
survey you completed on your first lab day.
-ID refers to each participant’s identification
number (this has nothing to do with student
ID numbers; it simply distinguishes one
participant from another).
-SchHrs is how many hours students
typically spend on school work each week
(including class time).
-Money is the degree to which students
agreed with the statement: “It is important for
me to make a lot of money” where 1=strongly
disagree, 4=neither agree nor disagree,
7=strongly agree.
-Education is the degree to which students
agreed with the statement: “My education is a
top priority in my life” where 1=strongly
disagree, 4=neither agree nor disagree,
7=strongly agree.
Psych 209/Kerr/Autumn 2010
2
THERE ARE THREE PARTS TO THIS ASSIGNMENT
PART 1. Draw a Scatterplot by Hand (2 points)
Use the attached worksheet (page 5) to draw a scatterplot of the correlation between ‘SchHrs’ and
‘Money.’ Put SchHrs on the x-axis and Money on the y-axis. Scale and label the axes appropriately.
You may use graph paper if you prefer.
PART 2. Excel Analysis of a Small Dataset (7 points total)
1. Enter the data from the table on page 1 into Excel. Use Excel to calculate the means, medians,
and standard deviations (=STDEVP) for the three variables. Round these statistics to two decimal
places and label your values. This example shows the correct format, but the numerical values are
fake: (1 point)
Mean
Median
SD
SchHrs
21.67
21.00
7.10
Money
3.50
2.00
0.88
Education
4.20
3.00
1.05
2. Use Excel to make a scatterplot like the one you drew by hand in Part 1. Put SchHrs on the x-axis
and Money on the y-axis. Label the axes with the variable names and ENTER YOUR NAME AND
STUDENT ID IN THE TITLE. Be sure your figure is scaled appropriately. (2 points)
3. Use Excel (=PEARSON) to calculate the Pearson Product Moment correlation coefficients
between:
a. SchHrs and Money
b. SchHrs and Education
c. Money and Education
Round the correlation coefficients to two decimal places and label your values. This example
shows the correct format, but the numerical values are fake: (2 points)
Correlation coefficient
0.65
-0.17
0.24
SchHrs and Money
SchHrs and Education
Money and Education
4. Type two sentences into the spreadsheet that report the correlation results for ‘SchHrs’ and
‘Money’. Describe the association between the two variables (i.e., describe the Pearson value and
scatterplot). Be sure to address the directionality and magnitude* of the correlation. (1 point)
5. Type two sentences into the spreadsheet that report the correlation results for ‘SchHrs’ and
‘Education’. As in item 4, describe the association between the two variables.* (1 point)
*When interpreting the magnitude (or strength) of your correlations, use the values in the table
below. For example, a value of r = -0.35 would be considered a medium (or moderate), negative
correlation. Note: These values are general guidelines and do not apply in every situation, but we
will use them for this assignment.
Correlation magnitude
Nonsignificant
Small (weak)
Medium (moderate)
Large (strong)
Negative values
-.09 to 0.0
-0.29 to -0.10
-0.49 to -0.30
-1.00 to -0.50
Positive values
0.0 to .09
0.10 to 0.29
0.30 to 0.49
0.50 to 1.00
Psych 209/Kerr/Autumn 2010
3
The Final Product of Part 2. All of Part 2 must appear as a readable Excel printout. If you print
in “landscape” mode, you may be able to fit all of Part 2 onto a single page, but this is not required.
However, make sure no individual table or graph stretches across multiple sheets. Check your final
printout and make sure it has the following:
o The assigned descriptive statistics (item 1), labeled and rounded (see example).
o The assigned scatterplot (item 2), correctly scaled and labeled. Make sure to include your
name and student ID in the title for full credit.
o The assigned correlation coefficients (item 3), labeled and rounded (see example).
o The assigned sentences about the relationships between the variables (items 4 and 5).
PART 3. Excel Analysis of a Large Dataset (6 points total)
Go to the class website: http://courses.washington.edu/psy209 and download the data file for this
part of the assignment. The file is under the heading Class Survey Data, and is named
Psych209_Autumn_2010_Survey.xls. This data file contains responses to the survey that students
completed on the first lab day. The dataset in Psych209_Autumn_2010_Survey.xls is much larger
than the dataset on page 1 of this assignment, but the process for analyzing the data is identical.
1. Use Excel (=PEARSON) to calculate the Pearson Product Moment correlation coefficients
between:
a. SchHrs and Power
b. Power and Money
Round the correlation coefficients to two decimal places and label your values. This example
shows the correct format, but the values are fake: (1 point)
SchHrs and Power
Power and Money
Correlation coefficient
0.05
0.46
Note:
-SchHrs is how many hours students typically spend on school work each week (including
class time).
-Money is the degree to which students agreed with the statement: “It is important for me
to make a lot of money” where 1=strongly disagree, 4=neither agree nor disagree,
7=strongly agree.
-Power is the degree to which students agreed with the statement: “It is important for me
to have a position of power and influence” where 1=strongly disagree, 4=neither agree
nor disagree, 7=strongly agree.
2. Using Excel, create a scatterplot of the correlation between SchHrs and Power. Put SchHrs on the
x-axis and Power on the y-axis. Label the axes with the variable names and ENTER YOUR NAME
AND STUDENT ID IN THE TITLE. Be sure your figure is scaled appropriately. (2 points)
3. Type two sentences into the spreadsheet that report the correlation result for SchHrs and Power.
Describe the association between the two variables (i.e., describe Pearson correlation and the
scatterplot). Be sure to address the directionality and magnitude* (or strength) of the correlation.
Refer back to the table on page 2 when writing your sentences. (1 point)
Psych 209/Kerr/Autumn 2010
4
4. Using Excel, create a histogram for ‘Religion’.
Note: Religion is the degree to which students agree with the statement “My religious/spiritual
values are a top priority in my life.” where 1=strongly disagree, 4=neither agree nor disagree,
7=strongly agree.
Label your axes appropriately and ENTER YOUR NAME AND STUDENT ID IN THE TITLE. (2
points)
Final Product for Part 3. All of Part 3 must appear as an Excel printout. If you print in
“landscape” mode, you may be able to fit all of Part 3 onto a single page, but this is not required.
However, make sure no individual table or graph stretches across multiple sheets. Check your final
printout and make sure it has the following:
o The assigned correlation coefficients (item 1), labeled and rounded (see example).
o The assigned scatterplot (item 2), correctly scaled and labeled. Make sure to include your
name and student ID in the title.
o The assigned sentences about the relationship between the variables (item 3).
o The assigned histogram (item 4), correctly scaled and labeled. Make sure to include your
name and student ID in the title.
________________________________________________________________________________
Formatting this assignmentFollowing the assigned format assures that your paper can be graded swiftly and fairly, without
complications. You will lose points for not following the format. Attach a cover page with a) Your
name and student ID, and b) Your TA’s first name and the time of day that your section meets
(e.g., “Matt 10:30”). A cover sheet helps us keep track of assignments and grades.
Put your work together in the following order: the cover page, Part 1 (the hand-drawn scatterplot –
use page 5 of this handout), Part 2 (Excel printout for small dataset), Part 3 (Excel printout for large
dataset).
PLEASE HAND WRITE YOUR NAME ON EVERY PAGE at the top right (to help us if the
pages separate). Staple everything together to help make sure this does not happen!!
CAUTION – Handwriting your name is NOT a substitute for the REQUIRED name/student ID
number entered into Excel for the scatterplot and histogram.
Getting help:
You are encouraged to talk about the assignment with others - including your classmates, TAs, peer
tutors, Dr. Kerr, and the consultants in the computer labs. However, the hand-drawn scatterplot,
Excel work, and written descriptions of the correlations must be your own. Sharing files and
copying calculations is not acceptable. Once more: To receive credit for Parts 2 and 3, the title of
the two scatterplots and the histogram MUST contain your NAME and STUDENT ID NUMBER.
If you work on the assignment in a computer lab on campus and need help with the specifics of
using Excel, we recommend working in the CSSCR computer labs for students on the first floor of
Savery in room 110 where consultants are available to assist you.
Psych 209/Kerr/Autumn 2010
5
NAME ______________________ Student Number_________________
TA's Name_____________
Section Time ______________
PART 1: HAND DRAW A SCATTERPLOT
Draw a scatterplot of the correlation between ‘SchHrs’ and ‘Money.’ Put SchHrs on the x-axis and
Money on the y-axis. Scale and label the axes appropriately. You may use graph paper if you prefer.
Y
0
X