Psyc 393 Fall 2011
Lab Exercise #2 – Sternberg Search
Due Dec 19 th at end of lab period
Resources Needed:
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Your CogLab e-registration code
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A Pharos Print Card (available from the Library)
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The CogLab manual (PDF on the class website)
• GraphPad Prism, available under CSUSM site license for Mac OS X and Windows from http://graphpad.com/paasl/index.cfm?sitecode=csusm
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Microsoft Word (or another document editor)
Review:
• read the CogLab tutorial on Linear Regression: http://www.graphpad.com/curvefit/linear_regression.htm
• read the background http://coglab.wadsworth.com/experiments/Sternberg.shtml
Run the CogLab experiment: Sternberg Search
Note: As you take the test, try to pay attention to your cognitions so you can answer the question in Exercise #1.
Log in with your CogLab information (ID/Password: not the same as your CSUSM ID!). You should see “Access
Approved” in green.
Click “Start experiment” when you are ready to begin. Once done, answer YES to add your data to global pool.
Exercise 1: Phenomenological Report
Write a one paragraph statement of your thoughts as you were taking the experiment. Did your performance get better
(or worse?) Was it easier (or harder) when the target was (or was not) in the memory set? Did you feel as if you were faster on the “Present” trials? Could you tell if you were using Serial Exhaustive vs. Serial Self-Terminating search?
Exercise 2: Data Collection and Entry into Prism
Goal – enter your individual data into a Prism sheet for later analysis.
• View your individual data in CogLab by clicking the “You can also view your own data” link (or, from the
CogLab Home Page / Student / Access your account, then use the “Get your own data” button)
• Open Prism
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Create a new Table & Graph – I mportant – what type of data sheet?
• There are 60 trials to enter. As in Lab #1, you need to split the data into two columns, based on the
Independent Variable (IV), but this time there is both an X and Y value to enter for each.
Note: CogLab has already graphed your data for you – refer to this for the next steps to see if you have graphed the correct information – however the CogLab graph is not the same format as you should make in exercise 3B.
Once you have your data entered, copy & paste the spreadsheet from Prism into Word.
Exercise 3A: Univariate Analyses – Histogram, Mean(SD)
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First, verify with the instructor or GA that your data has been entered properly before you proceed!
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In Prism, select your data table (it will be called “Data 1” by default)
• Click the “=” icon (Analyze)
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Choose “Column Analyses / Frequency Distribution”
• Select Only one of your Y columns (Column A only)
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Click OK, and again OK on the next screen (leave all Parameters as defaults)
• Find your histrogram (it will be in “Graphs” named “Histogram of Data 1”)
• Clean up your graph (label the X and Y axes, add a descriptive Title, etc.)
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Copy & Paste into your Word.doc, and add a Legend / Caption (e.g. “Graph X : blah blah”)
• Repeat for your 2 nd column of data so you end up with two histograms (one for each Y variable)
Exercise 3B : Multivariate Analyses : Linear Regression and graph for Both of your Y variables.
• Linear Regression o In Prism, select your data table (it will be called “Data 1” by default) o Click the “=” icon (Analyze) o Choose “XY analyses / Linear Regression” o Select Both columns (A and B) and hit OK o Options:
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Check “Compare : Test whether slopes and intercepts are significantly different”.
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All other options : defaults o You will end up with two result tables : “Tabular Results” (which shows the regression for each Y dataset) and a “Are lines Different?” result which compares the two.

o Write a textual description of the linear regression, as if you were writing a “Results” section.
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You will have two separate linear regressions – describe each one separately
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(N, r-square, r, and p value) - (Hint: how do you calculate the r value from r-squared?)
• Mean (SD) of each Y variable (hint: from exercise 2)
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Are the slopes of the two regression lines statistically different?
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XY Scatterplot with 2 Linear regressions o You should have a graph called “Graphs: Data1” which shows both linear regressions on the same graph. o Customize the graph so it is more readable (see next page for sample)
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Make the data points smaller and use “X” and “O” for the symbols
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Add color (Red = RT Absent, Green = RT Present)
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Label & title the graph
Make your graph look something like this (variations in data, labels, titles, etc. are ok)
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0 2 4 6
Exercise 4A, 4B – Repeat 3A and 3B using the grouped data (the data file will be provided by the instructor during the lab period)
Exercise 5 – Discussion
Write a brief (1-2 paragraph) summary of what you found – did the results support Sternberg’s hypothesis? Be specific about what statistical parameter was the key “finding” that did (or did not) support the hypothesis (was it the P value, the slope of line Y1 the slope of line Y2 or…?) Were your individual results consistent with the group results or did they differ? Given your individual experience while taking the task, what are some potential issues or confounds with the methods used in class?
Turning In: Please use the following header on page 1:
FirstName LastName
CogLab ID: (your coglab id)
Psyc 393 Lab #2 – Sternberg Test
Date: (today’s date)
Checklist – your assignment should have:
• Your Name and CogLab ID#
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Exercise 1 - One or more paragraph answer
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Exercise 2 - A data table with your individual data (1 X column, 2 Y columns)
• Exercise 3A – Two graphs (histrograms), one for each column of data
• Exercise 3B – One paragraph Results Section description of the linear regression results, univariate statistics, and one graph (XY Scatterplot with 2 regression lines)
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Exercise 4A, 4B – same as 3A, 3B
• Exercise 5 – One or two paragraph answer