Factors Affecting Stress Exercise
Introduction to Experimental Psychology II HC 212, Spring 1999
(adapted from 202 lab developed by Dr. Sara Hodges)
Lab Objective: Psychologists often develop hypotheses based upon observations of the world
around them, and then systematically collect data to test these hypotheses. In this lab, you will :
I. Develop a hypothesis about a stressor in your life
II. Collect data on yourself
III. Compute the correlation between your stressor and your stress level
IV. Share data with other people in your group
V. Submit these results to us
In lab today, you will do I. You will be responsible for doing II., and III. on your own outside of
class (instructions are listed below) in the next week. Then, during the next lab, you will discuss
your results (IV.) with other lab members. Finally, you will submit your results (V.) to me at the
end of the second lab.
Bring a copy of your raw data (the ratings of your two variables), your worksheet from today's
lab, a print out from the correlation matrix web page (if you choose to use the web page), and
your correlation coefficient to lab with you on Wednesday, April 7.
I. STRESS! Pick a variable
Many people, including college students, report feeling a lot of stress. Different things stress out
different people. What do you think affects you? You will work in groups to discuss stressors,
that is, variables that you think affect your stress levels. It has to be something you can measure,
and to which you can assign a numerical value.
After group discussion, you will pick out a variable for yourself. The variable you pick may be something you measure by self-rating, as would be the case if you think that how tired you are feeling affects how stressed you feel. If you used this variable as your stressor, you would have to designate a scale on which to rate how tired you feel each day. For example, the scale could take the following form:
1 = not at all tired
2 = slightly tired
3 = somewhat tired
4 = very tired
5 = extremely tired
The scale above (known as a Likert scale) is very subjective. You might want to specify what each category means. For example, During the last hour, I felt
1 = not at all tired: felt well-rested, felt alert
2 = slightly tired: yawned only a few times, felt mostly rested
3 = somewhat tired: yawned several times, had to sit down to rest at least once
4 = very tired: had to rest a lot, yawned frequently
5 = extremely tired, activities limited by fatigue
Whatever you decide, make sure you understand what the stressor is, and how to rate it. Fill out
the attached worksheet to specify your stressor.
II. Daily Stress Diary
Three times each day, for 5 consecutive days, you will keep track of your stress level, and your
variable (whatever you pick). You should pick three consistent times each day to make your
ratings (for example, before breakfast, at 2pm, and just before going to bed).
Given that stress is largely a subjective construct (i.e., you are as stressed as you feel), we will
use a subjective rating scale to rate stress, and everyone will use the same scale:
1 = No stress
2 = Minimal stress
3 = Moderate stress
4 = Heavy stress
5 = Maximum stress
You might want to specify what each category means for you depending on how you experience
stress (for some people, heavy stress might involve feelings of nausea; others might sweat
The easiest way to record the data would be to put four column headings on a sheet of paper,
labeling the first column 'Date', the second 'Time of Day, the third 'Stress' and the fourth
'Stressor' (or what your specific stressor is). After recording the date and time of day, you will
write down two numbers, three times each day: one will be a rating of your stress level, and the
other a rating or count of your stressor.
III. Computing the correlation
Once you have the complete group data, you will compute a correlation between the two
variables. A correlation coefficient (review pp. 50-51 in your text) is a numerical rating of the
degree to which the two variables co-vary. It can be negative (which means that when one
variable goes up, the other goes down) or positive (which means that when one variable goes up,
the other also goes up). The further the correlation coefficient is from zero, in either a positive or
negative direction, the higher the correlation between the two variables. A correlation of -1.0 or
1.0 is a 'perfect' correlation, meaning you can exactly predict the value of one variable if you
know the value of the other variable. The easiest option for computing a correlation coefficient is
to go to the following web site: http://www.stat.ucla.edu/calculators/correlation.phtml
Scroll down to where it says 'Input both Variables' in bold. In the two columns provided for you,
enter your stress level in one column, and your ratings of your stressor in the other. Make sure
that both variables for the same day and time are across from each other (i.e., on the same line).
Use the mouse, the arrow keys, and the return key to move around. When you are finished
entering your data, click on 'submit.' Now, scroll down to where it says 'Statistics' in bold. Look
for the value next to 'Correlation X and Y' (NOT 'Covariance X and Y'). This is your correlation
Although using the web page is very simple, there are other options for computing the correlation
coefficient. If you have a calculator that does statistical functions, it may be possible to use your
calculator. If you use a spreadsheet on your computer, you may be able to compute a correlation
using it too. Virtually any introductory statistics textbook will also include the formula for
computing a correlation coefficient by hand.
Compute the correlation, and bring your raw data, your correlation, and any calculations with you
to your lab on April 7.
IV. Sharing data
Next Tuesday, you will form groups in class. In lab next Wednesday you will share your data
and results with other members of your group.
Stress Lab Worksheet
1. List the variable you picked as a potential stressor (describe your variable):
2. Do you think the stressor has a positive relationship with stress (when ratings of your stressor
go up, stress level goes up), or a negative relationship with stress (when ratings of your stressor
go down, stress level goes up)?
3. Provide the following information about your rating scale below:
a) What are the minimum and maximum values?
b) What are the 'anchors' (verbal labels describing the numerical values)?