Writing with APA style (cont.) &

Experiment Basics: Variables

Psych 231: Research Methods in Psychology

Announcements

Journal Summary assignment due in labs this week

Bring your textbook (or APA style manual if you’ve got one) to lab this week (using chapter 16 on APA style)

Body

• Introduction• Background• Literature Review• Statement of purpose• Specific hypotheses (at least at conceptual level)

Body

Participants• How many, where they were selected from, any special selection requirements, details about those who didn’t complete the experiment

Methods (in enough detail that the reader can replicate the study)

Body

Design (optional) • Suggested if you have a complex experimental design, often combined with Materials section

Methods (in enough detail that the reader can replicate the study)

Participants

Body

Apparatus/Materials Procedure

• What did each participant do? Other details, including the operational levels of your IV(s) and DV(s), counterbalancing, etc.

Methods (in enough detail that the reader can replicate the study)

Participants Design

Body

Results (state the results but don’t interpret them here) Verbal statement of results Tables and figures

• These get referred to in the text, but actually get put into their own sections at the end of the manuscript

Statistical Outcomes• Means, standard deviations, t-tests, ANOVAs, correlations, etc.

Figures and tables

These are used to supplement the text. To make a point clearer for the reader.

Typically used for:• Patterns of results • The design• Examples of stimuli

Chapter 8

Body

Discussion (interpret the results) Relationship between purpose and results

Theoretical (or methodological) contribution

Implications Future directions (optional)

Checklist - things to watch for

#1 Clarity - say what you want to say Acknowledge the work of others (avoid plagiarism)

Active vs. passive voice (avoid passive)• Active: “Bock and Coey (2003) hypothesized that speakers use to much passive voice …”

• Passive: “It was hypothesized by Bock and Coey (2003) that speakers use to much passive voice…”

Checklist - things to watch for

Avoid biased language• APA guidelines:

• Accurate descriptions of individuals (e.g., Asian vs. Korean)

• Be sensitive to labels (e.g., “Oriental”) Appropriate use of headings Correct citing and references Good grammar, spelling, etc.

So you want to do an experiment?

What behavior you want to examine Identified what things (variables) you think affects that behavior

You’ve got your theory.

So you want to do an experiment?

You’ve got your theory. Next you need to derive predictions from the theory. These should be stated as hypotheses.

In terms of conceptual variables or constructs

So you want to do an experiment?

You’ve got your theory. Next you need to derive predictions from the theory.

Now you need to design the experiment. You need to operationalize your variables in terms of how they will be:• Controlled• Manipulated• Measured

Be aware of the underlying assumptions connecting your constructs to your operational variables

An example

Hypothesis: Eating candy with peanuts improve memory performance

How might we test this with an experiment?

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Constants vs. Variables

Characteristics of the psychological situations Constants: have the same value for all individuals in the situation

Variables: have potentially different values for each individual in the situation

Constants: • M&Ms are eaten

Variables:• Type of M&M: peanut vs plain• Memory performance

Variables

Conceptual vs. Operational Conceptual variables (constructs) are abstract theoretical entities

Operational variables are defined in terms within the experiment. They are concrete so that they can be measured or manipulatedConceptual

Peanut candies

Memory

Operational

Peanut M&Ms

Memory testUnderlying assumptions

Variables

Independent variables (explanatory)

Dependent variables (response) Extraneous variables

Control variables Random variables

Confound variables

Independent Variables

The variables that are manipulated by the experimenter (sometimes called factors)

Each IV must have at least two levels Remember the point of an experiment is comparison

Combination of all the levels of all of the IVs results in the different conditions in an experiment

Independent Variables

1 factor, 2 levels Condition 1Condition 2

Factor A

1 factor, 3 levels

2 factors, 2 x 3 levels

Cond 1

Factor A

Cond 3Cond 2

Cond 1

Factor B

Cond 3Cond 2Factor A Cond 4 Cond 6Cond 5

Manipulating your independent variable

Methods of manipulation Straightforward manipulations

• Stimulus manipulation - different conditions use different stimuli

• Instructional manipulation – different groups are given different instructions

Staged manipulations • Event manipulation – manipulate characteristics of the context, setting, etc.

Subject manipulations – there are (pre-existing mostly) differences between the subjects in the different conditions (leads to a quasi-experiment)

Choosing your independent variable

BottlecapsPeanut M&Ms

1 IV: Candy type (3 levels)

• What about our candy experiment?

Plain M&Ms

Dependent Variables

The variables that are measured by the experimenter

They are “dependent” on the independent variables (if there is a relationship between the IV and DV as the hypothesis predicts).

Choosing your dependent variable

How to measure your your construct: Can the participant provide self-report?

• Introspection – specially trained observers of their own thought processes, method fell out of favor in early 1900’s

• Rating scales – strongly agree-agree-undecided-disagree-strongly disagree

Is the dependent variable directly observable?• Choice/decision (sometimes timed)

Is the dependent variable indirectly observable?• Physiological measures (e.g. GSR, heart rate)• Behavioral measures (e.g. speed, accuracy)

Choosing your dependent variable

Conceptual level: Memory Operational level: Some kind of memory test

Memorize a list of words while eating the candy Then 1 hour after study time, recall the list of words Measure the accuracy of recall

• What about our candy experiment?

Extraneous Variables

Control variables Holding things constant - Controls for excessive random variability

• Number of M&Ms consumed• Time of day test taken

Extraneous Variables

Random variables – may freely vary, to spread variability equally across all experimental conditions Randomization

• A procedures that assure that each level of an extraneous variable has an equal chance of occurring in all conditions of observation.

• On average, the extraneous variable is not confounded with our manipulated variable.

• What your participants ate before the experiment

Control your extraneous variable(s)

Can you keep them constant? Should you make them random variables? Two things to watch out for:

Experimenter bias (expectancy effects)• the experimenter may influence the results (intentionally and unintentionally)

• E.g., Clever Hans • One solution is to keep the experimenter “blind” as to what conditions are being tested

Demand characteristics – cues that allow the participants to figure out what the experiment is about, influencing how they behave

Confound Variables

Confound variables Other variables, that haven’t been accounted for (manipulated, measured, randomized, controlled) that can impact changes in the dependent variable(s)

Next time

Read chapters 3 & 5. Bring your textbook and/or APA Publication Manual to lab (if you’ve got one)

Don’t forget your first journal summary is due this week in lab