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 uncontrollably).

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 coefficient.

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)?