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Examinations Assignments

Exam #1 = 35 pts. Introduction and References = 25 pts. Exam #2 = 35 pts. Methods section = 25 pts. Exam #3 = 35 pts. Results section = 20 pts. Exam #4 = 35 pts. Final paper = 40 pts. Lab activities = 10 pts. Participation (Research proj) = 10 pts.

Summary presentation = 10 pts. _______ _______ Total Exam pts = 140 Total assignment pts = 140 Total points for the course = 280

30 pts20 pts

Assignments

vMWMDrop lowest test score

105 130235

Revised Grading Scheme Revised Grading Scheme

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Chapters 12 & 15

And so much more

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Large and Small N designs

Small N

• one or a few subjects

Large N

• Greater than a few subjects (often multiple groups)

• most common technique used in research design

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Large N Designs

• Gained in popularity after Sir Ronald Fisher invented the analysis of variance in the 1930s

• Easier to generalize with more than one subject (greater external validity)

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Why even use small N?

• Precision – pooling or combining data can obscure the results of individual subjects

• You may miss effects by pooling data across individuals.

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Subject 1 Subject 2 Combined

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Why even use small N?

• Another example where pooling data led to a misinterpretation of what subjects had or had not learned?

• Hint: a series of water maze studies on the effects of partial reinforcement (PR)– How many subjects in the PR group?– What data was pooled?– What was discovered by de-aggregating the

data?– What’s the big picture lesson?

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The BIG PICTURE lesson• Large N’s aggregate over subjects.• Smaller N studies sometimes aggregate over

time.• Both have the potential to loose fidelity

Mirriam-Webster OnlineMirriam-Webster Online

a: the quality or state of being faithful b: accuracy in details : exactness 2: the degree to which an electronic device (as a record player, radio, or television) accurately reproduces its effect (as sound or picture)

From Wikipedia, the free encyclopedia

High fidelity (disambiguation)

High fidelity or hi-fi is most commonly a term for the high-quality reproduction of sound or images

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Small N Designs

• Also used for practical reasons– Only a few patients in clinical research for a

rare disease, plenty with common ones– Animals may be expensive (especially those fancy rats)

Just the crowd I want to hang

around and get advice from

So, it’s ideal for poor researchers with restricted or limited access to human patients and/or those that may lack motivation to collect acceptable amounts of data in order to do a real study deemed credible by other scientific peers!

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Small N Designs

Popular in:• Clinical and animal research• Laboratory and field studies• Psychophysics• Studies of learning

• Used most extensively in operant conditioning research

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ABA Design

• The return to baseline in the ABA design tests whether B had an effect or whether another extraneous variable confounded the study.

• Thus, the effect of B, the experimental treatment, must be reversible

• it is also called a reversal design

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Variations of the ABA Design

• ABABA – two treatments and two returns to baseline – can detect cumulative effects of the treatment

• ABACADA – multiple experimental conditions - B, C and D represent different treatments

• AB design – sacrifice the return to baseline if it would harm the subject (e.g., behavior modification worked in reducing self-injurious behavior)

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Variations of the ABA Design

A Swedish A Swedish design that design that only made only made sense in the sense in the drug-induced drug-induced haze of the haze of the 70s disco era.70s disco era.

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Variations of the ABA Design

• Multiple baseline design – a series of baselines and treatments are compared, but once a treatment is established it is not withdrawn (e.g. AAABBB no more As)

• Discrete trials design – does not rely on baselines at all, but compares performance across treatment conditions (e.g. BCDE) a BC design would be analogous to what large N design?

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Variations of the ABA Design

• After “A”, never After “A”, never return to baseline return to baseline

• skip all the boring B skip all the boring B condition stuff and condition stuff and go right for the CDC go right for the CDC conditions that put conditions that put you on a fast track to you on a fast track to the land down-the land down-under…under…

• Apply thunderbolt Apply thunderbolt between C and D.between C and D.

AC/DC – a.k.a, the “Indiscrete trials design”

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B. F. Skinner

• Studied changes in the rate of behavior (e.g., a rat lever pressing for food)

• by careful, continuous measurement of a single subject over time.

The control and experimental conditions are given to the same subject at different times

ABaseline

BExperimental

ABaseline

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Evaluating the Experiment

• Internal validity – was the experiment free of confounding?

• Manipulation check – assesses how successfully the experimenter manipulated the situation she or he intended to produce.

• Pact of ignorance – subjects who have guessed the hypothesis might try to hide the fact because they know that their data might be discarded.

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Statistical problems

• Statistical conclusion validity – are conclusions about the statistical results valid?

• Did you use an appropriate test?• Too many a priori tests – increases the

chance of making a Type 1 error. • Small effect size – the results can be

significant but not very meaningful if the effect size is small.

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External validity

• Two requirements:– The experiment is internally valid – And can be replicated

What form of validity is a prerequisite for another form of validity?

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Research significance

• Are the results consistent with prior studies?

• Do the results extend our knowledge of the problem?

• Are there any implications for broader theoretical issues?

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Multivariate Designs

• Involve multiple variables studied concurrently– MANOVA (multiple DVs)– Multiple correlation – Factor analysis

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Unobtrusive measures

• Specific procedures for measuring a subjects behavior without them knowing that their behavior is being measured– Greater external validity because the

behavioral data is similar to behavior occurring outside the experiment

– E.g., a field experiment• Manipulate antecedent conditions• Observe outcomes in natural setting

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Nonsignificant results

You should reconsider:

• The experimental hypothesis

• The procedures used in the study

• The possibility that a Type 2 error occurred