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Chapter 2 - The Ways and Means of Psychology Slide 1
Chapter 2
The Ways and Means of Psychology
Chapter 2 - The Ways and Means of Psychology Slide 2
The 3 Major Types of Scientific Research are:
Naturalistic Observations involve observing people or animalsin their natural environment with as little involvement as possible
Correlational Studies are often observational, but also involve the measurement and examination of variables that may berelated to certain behaviours
Finally, experiments use active manipulation to gain a betterunderstanding of how certain variables effect behaviour
The Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 3
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 4
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 5
Steve shows you his “vacation video” of a shark diveas a way of illustrating the continuous nature of naturalistic observations
Via the “chainmail” suit, explains how naturalistic observations can lead the formation of a hypothesis
Follows this up with the “shark electrical experiment video” to show how an experiment can then be done to test the hypothesis
Examples
Chapter 2 - The Ways and Means of Psychology Slide 6
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 7
Some Basic Terminology (in sharky context)
Variable - Anything that can take on multiple values
Independent Variable - A variable that is manipulated by the experimenter (presence or absence of an electric field)
Dependent Variable - A variable that is measured during an experiment … typically an index of behaviour (some measure of avoidance behaviour)
Designing an Experiment
Chapter 2 - The Ways and Means of Psychology Slide 8
Often experiments involve a contrast between the behaviour of subjects in a control condition (a group or condition in which the critical manipulation is not present) with an experimental group (a group or condition where the critical manipulation is present)
For example, the experimental condition of the shark study was when the electric field was on, the control condition was when it was off
Designing an Experiment
Chapter 2 - The Ways and Means of Psychology Slide 9
Often our theory involves general ideas, but experiments require specific variables … thus we must define our concepts operationally, in terms of some variables that can be measured or manipulated
e.g., students who are encouraged to actively participatein classes will learn better
Operational Definitions
Chapter 2 - The Ways and Means of Psychology Slide 10
Often our theory involves general ideas, but experimentsrequire specific variables … thus we must define ourconcepts operationally, in terms of some variables that can be measured or manipulated
e.g., students who are encouraged to actively participatein classes will learn better
Making course notes available?Verbally encouraging students to participate?
Operational Definitions
Chapter 2 - The Ways and Means of Psychology Slide 11
Often our theory involves general ideas, but experimentsrequire specific variables … thus we must define ourconcepts operationally, in terms of some variables that can be measured or manipulated
e.g., students who are encouraged to actively participatein classes will learn better
Final marks?Student evaluations of learning?
Operational Definitions
Chapter 2 - The Ways and Means of Psychology Slide 12
The validity of an experiment refers to how well the operational definitions capture the concept of interest
Manipulation checks can be used to test the validity of independent variables
The validity of an experiment is also strengthened if other operational definitions of the same concept(s) provide similar results (i.e., converging evidence)
Validity of an Experiment
Chapter 2 - The Ways and Means of Psychology Slide 13
In order to attribute the results of the experiment to the independent variable that was manipulated, it is important that the critical conditions were systematically different only in terms of that variable
If some other variable also differed across conditions, then the two variables are said to be confounded, and it is impossible to attribute the results to either variable in a convincing manner
e.g. - can you tell me how to get to Sesame Street?
Confound it!
Chapter 2 - The Ways and Means of Psychology Slide 14
Sometimes it is necessary to use counterbalancing techniques to avoid confounds
For example, the Stroop example we did last class actually included a confound … practice (subjects usually get faster at any task with practice on that task)
Solution … half the subjects get the congruent list followed by the incongruent … and half get the incongruent followed by the congruent
Counterbalancing to Avoid Confounds
Chapter 2 - The Ways and Means of Psychology Slide 15
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 16
If you measure your height over and over, you’ll tend to get the same height each time … rulers are reliable
What if you wrote the “same” test over and over, would you expect to always get the same mark? And what if the conditions of testing changes with each test?
It is important that variables be measured as reliably as possible when an experiment is performed … the more reliable a variable can be measured, the higher the chance of finding a difference/relation if it exists
Reliability
Chapter 2 - The Ways and Means of Psychology Slide 17
Some variables can be measured objectively (e.g., reactiontimes), others are more subjective (e.g., babies reactions)
It is harder to reliably measure a subjective variable, and often one must use multiple raters and examine inter-rater reliability to insure reliability of measurement
This is done by seeing how often independent raters agreein their measures … low agreement = poor reliability
Subjective Measures and Inter-rater Reliability
Chapter 2 - The Ways and Means of Psychology Slide 18
Note the difference between reliability and validity
Reliability is the likelihood of getting the same result if some variable is measured on multiple occasions
Validity refers to how well some variable reflects somepsychological concept
e.g., IQ tests of Intelligence
Reliability versus Validity
Chapter 2 - The Ways and Means of Psychology Slide 19
Often independent variables are confounded because of subject differences across the groups
The best way to avoid subject differences is to use random assignment
If random assignment is combined with fairly large sample sizes, the groups should not be systematically different in terms of the variables you know to be relevant AND the ones you don’t know about
The Importance of Random Assignment
Chapter 2 - The Ways and Means of Psychology Slide 20
Subjects hardly ever just go along with an experiment …rather, they never trust the experimenter, and almost always believe there is more to the experiment than the experimenter lets on (sometimes they are right!)
As a result, they do not behave “naturally”, but instead they try to figure the study out, and their behaviour is partially a function of their hypotheses about the exp
An experiment must do all that is possible to avoid such expectations to bias the results of their study
Those Pesky Subjects!
Chapter 2 - The Ways and Means of Psychology Slide 21
One way to try preventing a subject’s expectations from “causingan effect” is to not allow the subject to figure out what conditionof an experiment they are in:
e.g., subliminal perception “weight loss” tapes
… placebo idea
Thus, subjects in both the experimental and control groups mightexpect something, but there is no reason to believe that expectationswould be different across the conditions
… food is crap ...
Single Blind Studies
Chapter 2 - The Ways and Means of Psychology Slide 22
Sometimes it is not enough to have just the subject “blind”to what condition they are in, as it is possible that theexperimenter might react differently to subjects dependingon which condition they are in
In those cases it is sometimes optimal to have the experimenter“blind” as well throughout the course of the experiment
I have no idea!Where am I?
Double-Blind Experiments
Chapter 2 - The Ways and Means of Psychology Slide 23
> Subjects cannot be coerced into participating in experiments (hence course credit in A01)> Subjects must be told the ethically relevant aspects of the experiment, then give their informed consent
Deception is justified, as long as:> participant is debriefed after the study> does not otherwise harm the subject either
psychologically or physically> the dignity of the subject is maintained
Confidentiality of data is also necessary
A Question of Ethics - Human
Chapter 2 - The Ways and Means of Psychology Slide 24
Animals must be treated “humanely” in research settings> no unnecessary suffering> approved procedures for surgery and the like
Animal research should only be conducted if it is worthwhile> what is worthwhile?> the trend towards “simulated” rats
Issue of the treatment of pets versus research animals
A Question of Ethics - Non-Human
Chapter 2 - The Ways and Means of Psychology Slide 25
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 26
In my statistics class (PsyB07) I give the students a questionnaireon the first day, and use the data from this questionnaire throughoutthe class to demonstrate concepts
One of the things I ask them is how old they are. Here are some data
21, 20, 23, 21, 23, 22, 20, 21, 22, 22, 21, 25, 19, 22, 21, 23, 26, 24
OK, now what?
Statistics
Chapter 2 - The Ways and Means of Psychology Slide 27
Usually the first step to analyzing the data is to describe thedata by boiling down to certain descriptors (describe someone)
The usual suspects:
Frequency Tables and HistogramsMeasures of Central Tendency - Mean, Median, ModeMeasures of Variability - M.A.D. and Variance
Sometimes when we measure more than one variable, we wantto know something else too: Are the variables related?
Scatterplots, correlations
Descriptive Statistics
Chapter 2 - The Ways and Means of Psychology Slide 28
Age Frequency
19 1 20 2 21 5 22 4 23 3 24 1 25 1 26 1 0
1
2
3
4
5
19 20 21 22 23 24 25 26AGE
Fre
quen
cy
Frequency Tables and Histograms all you to depict all the data ina fairly concise way
Frequency Tables and Histograms
Chapter 2 - The Ways and Means of Psychology Slide 29
Sometimes we want to communicate the data in an even brieferform … one characteristic we often choose to communicate issome measure of “middle” to show a representative point
Mean - The point that is the minimum possible distance from all the other points in the sample
Median - The point that have the data points lie above, and half lie below
Mode - The most frequently occurring data point (or observation)
Measures of Central Tendency
Chapter 2 - The Ways and Means of Psychology Slide 30
Another characteristic we often which to quantify is the extentto which our data points lie close to the middle point
e.g., 18, 19, 20, 21, 22 vs. 5, 12, 20, 28, 35
M.A.D. - The mean absolute deviation of each data point from the mean of the numbers
Variance - The average squared deviation of each data point from the mean
Measures of Variability
Chapter 2 - The Ways and Means of Psychology Slide 31
Quite often our end goal is not merely to measure some variable but, rather, we wish to compare different groupsto see if they differ in terms of some variable
The tests we do to look for differences fall underthe heading termed “inferential statistics” and include suchthings as t-tests, z-tests, analysis of variance, and correlations
These are statistical procedures we use to eventually make inferences about how some variable affects the behaviour ofour population of interest
Inferential Statistics
Chapter 2 - The Ways and Means of Psychology Slide 32
Observed Difference
Difference That Would be Expected by Chance
> If large, we have an effect> If not, we don’t
A Taste of Statistical Logic
Chapter 2 - The Ways and Means of Psychology Slide 33
Observed Difference
Difference That Would be Expected by Chance
> If large, we have an effect> If not, we don’t
Difference between mean height of 6 males vs. 6 females
A Taste of Statistical Logic
Chapter 2 - The Ways and Means of Psychology Slide 34
Observed Difference
Difference That Would be Expected by Chance
> If large, we have an effect> If not, we don’t
Difference between mean height of 6 males vs. 6 females
Average difference between mean height of 6 randomlyselected people, and 6 other randomly selected people
A Taste of Statistical Logic
Chapter 2 - The Ways and Means of Psychology Slide 35
1. Identify the problem and formulate cause-effect hypotheses2. Design the experiment (PsyB01)3. Perform the experiment4. Evaluate the hypothesis on the basis of the obtained data (PsyB07)5. Communicate the results (PsyC02)
Plug for C90 & C93s
Rules of the Scientific Method
Chapter 2 - The Ways and Means of Psychology Slide 36
Publications- APA formatted manuscripts- The peer-review process- lag
Conference Presentations - Typical Format
Invited Talks
Communicating the Results