AP Psych Prep 2 (Part II) - More Methods, Statistics

8/13/2019 AP Psych Prep 2 (Part II) - More Methods, Statistics

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AP Psych. Prep. 2

Part II: More

ResearchMethods,Statistics


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Other Research Methods

The experimental method can be veryvaluable because it can show us theCAUSE if we are very careful in ourdesign.

But sometimes experiments areimpossible, or not well matched to the

topic or level of detail we are studying.

So we have a few other methods we canuse


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Correlational Method

Correlation a measure of therelationship between two variables. (nomanipulation, so no real I.V.)

Sometimes we cant assign participants togroups (e.g. boys and girls).

NOTE: if we do an experiment with pre-made groups like this, its called pseudo-experiment or ex post facto study.


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Correlational Method

Or sometimes its unethical to assignparticipants to groups. E.g. smokers vs.not smokers, victims of violence vs. notvictims

Correlational method involves measuringtwo variables, and calculating a correlation

coefficient, which is a number that tells usabout the strength and direction of therelationship between the them. (Seestatistics below)


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Survey Method

NOTE: Survey Method vs. Survey tool -We can use surveys as a tool in othertypes of methods (e.g. experimental).

Survey METHOD a type of correlationalmethod where you use give participants asurvey and then correlate variables to find

relationships.


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Survey Method

Survey method can be very easy andcheap to do.

But some negatives to this method: Confounding variables

Random sampling is difficult

Low response rate

People can lie


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Statistics (stats)

We use statistics to describe and makedecisions when we do scientific research.

1. Descriptive statistics stats thatdescribe a set of data.

1A. Frequency Distribution grouping

participants by some characteristic (e.g.what kind of phone do people own)


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We can Graph frequency distributions

Histogram (bar graph):FrequencyPolygon:


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1B. Measures of Central Tendency

MofCT try to mark the center of adistribution of numbers.

Mean average of the numbers

Median central score of orderednumbers; if odd number of values, halfway between middle numbers

Mode the most common number; canhave morethan one mode (bimodal, etc)

E.g. 6, 7, 7, 8, 8, 9, 9, 9, 10


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Outliers and Skewed Distributions: One or more veryhigh or very low scores will skew a distribution. Canbe skewed with a right tail (positive or right skew)

or left tail (negative or left skew)


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1C. Measures of Variability

Measures of Variability try to show howspread out a distribution is.

Measures of Central Tendency cant tell usabout thesedifferent shapes.

E.g.


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1C. Measures of Variability

Range the distance between the highestand lowest numbers

Variance and Standard Deviation twomeasures of the average distancebetween the data points and the mean(average)

Standard Deviation = Variance

High # = more spread out


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Normal Curve / Normal Distribution

Closely connected to measures ofvariance.

Normal Curve special bell-shaped curvewith certain number of scores within

different ranges.


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1 S.D.= zscore of1


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If your z-score on a test is +2, what

percentage of competitors did you do scorebetter than?

____________________________________

If the standard deviation is 25, and the meanis 100, what number will be at z score -3?____________________________________

What is the z score below which the lowest 16percent of people will score?____________________________________


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Correlation Coefficient

Correlation coefficient number thatmeasures the relationship between twovariables.

Can be positive or negative. Positivemeans when one variable increases, sodoes the other. Negative means when onegoes up, the other goes down.

A score of 0 means theres no relationship.


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Value of the correlation coefficient indicates howstrong the connection between the variables is.Closer to -1 or +1 are strong, farther are weaker.


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Correlation Coefficient

Important Notes:

CORRELATION does NOT equalCAUSATION.

Even if we find a perfect -1 or +1correlation between two variables, we CANNOT tell anything about the cause of therelationship.

** Shark Attacks and Ice Cream Sales **

Also, strong correlation positive

correlation


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2. Inferential Statistics

Inferential Stats help us decide if thedifferences we see in our numbers are realdifferences between our experimental andcontrol groups, and if we should

generalize our results to the widerpopulation.

Helps us answer: Is our result due tosampling error? Due to chance? Due tosmall sampling size?

Or is it because of a real difference?


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Larger sample size, and larger differencebetween the exp. and control groupsmake it more likely we will find a stat.significant result

Many tests that do this. Two examples: T-tests

ANOVA (Analysis of Variance)

These tests give us a pvalue.

Smaller pvalue = less likely due tochance


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Scientists generally agree that a pvalue of.05 or less means we have a statisticallysignificant result. (A real differencebetween our groups)

p= .05 means that only 5% of the timeour result is due to chance. I.e. one timeout of 20 trials.

We can also make p values for correlationcoefficients; see if our sample size waslarge enough, how sure we can be thatour result is real, etc.


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We are never 100% sure, but if we arevery careful in our experiment design, andtest multiple times and find low pvalues,we start to feel confident that we are

seeing a real explanation, a real cause.

Question: What do we think if we get a pscore of .10 ? __________________

Of .055 ? __________________

Of .005? __________________


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Research Ethics

Also very important.

APA sets ethical guidelinesfor all psych research.

All studies must be approved by

Institutional Review Boards (IRB) Submit proposal of procedure and ethical

protections, and IRB will approve or deny


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Research Ethics - Animals Must have scientific purpose

Must answer an important question Animals must be best for the question

Must care for and house animals

humanely Get animals legally, from approved

sources

If you MUST use wild animals, catch in a

safe and humane way Study must employ the absolute

LEAST amount of suffering possible


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Research Ethics - Humans

Must be voluntary - cant force or coercepeople to participate

Informed Consent person must

understand and agree to participate.Sometimes we can deceive a little bit (ifwe need to) but we need to be verycareful.


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Anonymity / Confidentiality protectidentity and personal information.

Anonymity name and data cant be

connected Confidentiality canbe connected, but

promise not to identity the person


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Risk cant put participants in a lot ofrisk. Long term mental or physical harm isnot allowed.

Temporary stress or discomfort isallowed,if its necessary for the specific question.E.g. ice pain studies


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Debriefing after study, must explainstudy and give ways to contact researcherlater. Offer to give results to participantswhen study is over.

If deception was used, must reveal andexplain why you needed to do it that way.

Some studies we talk about would not beallowed by IRBs today. Stronger ethicalguidelines

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AP Psych Prep 2 (Part II) - More Methods, Statistics