CHAPTER 20

Psychological Research and Statistics

Objectives

Describe the process of psychological research

Name the different types of psychological research and some of the methodological hazards of doing research

Describe descriptive and inferential statistics

Name specific research methods used to organize data

Gathering Data

How do psychologists collect information about the topic they’ve chosen to study?

Gathering Data

Validity – verifying that a claim is correct, or disproving it A claim cannot be valid until it has been

repeatedly tested and found to be trueExample: Fashion magazine

advertisements (“thicker” hair, no wrinkles, rapid weight loss)

Innocent until proven guilty – have to be found guilty in order for your arrest to be valid

Gathering Data

Sample – relatively small group out of the total population

Population – an entire group as a whole Sample must be representative of the

population If a sample is not representative, then it

is biasedHow can researchers avoid bias?

Gathering Data

What does correlation mean? The degree of relatedness between

two sets of data

Two types - positive correlation & negative correlation

Gathering Data

IQ scores and academic success – positive correlation (direct relationship) The higher your IQ, the higher your

grades

Car speed and time it takes to travel somewhere – negative correlation (inverse relationship) - as car speed increases, time it takes to reach your destination decreases

Your turn!

Hours in the sun and chance of sunburn Positive correlation

Amount of exercise and % body fatNegative correlation

Mr. Cline’s high school GPA and your high school GPA

no correlation

Experiments

Why do researchers choose experimentation over other research methods? Researchers can control the situation.

The goal of research is to prove or disprove a . . .

Hypothesis

Experiments

Variables – conditions and behaviors that are subject to variation/change

Two types of variables – independent and dependent IV – manipulated variable in order to

view its effects DV – dependent upon the IV –

affected by it

Experiments

Experimental group – consists of subjects who undergo the experimental treatment – variables are applied to this group

Control group – consists of subjects who do not receive experimental treatment Why is this group necessary?

Smile break

Experiments

Naturalistic observation – viewing the subjects of an experiment in their natural habitat IMPORTANT: Subjects CANNOT

know they are being watched! Why is this important??

ACTIVITY TIME!

Experiments

Case study – a scientific biography of a group or person Most use long-term research to

gather tons of data in order to generate new hypotheses

Stanford Prison Experiment

Experiments

Surveys – an interview/questionnaire that gathers data on the attitudes, beliefs, and experiences of large numbers of people

Experiments

Longitudinal studies – covers a long period of time

Psychologists study subjects over regular intervals for a period of years Allows for examination of

consistencies and inconsistencies

Experiments

Cross-sectional studies – individuals are organized/studied on the basis of age

Example – Milgram Shock Experiment

Avoiding Errors

How can researchers avoid errors while doing research? self-fulfilling prophecy - Researchers finding

what they want to find, while overlooking contrary evidence

Example experiment – testing a new medicine Single Blind – subjects do not know if they

have a placebo or the real thing Double Blind – subjects AND experimenter

have no knowledge of who has the real medicine/placebo

Statistics

A branch of mathematics that enables researchers to organize and evaluate the data they collect

Smile Break

Statistics

Descriptive statistics – listing and summarizing data in a practical and efficient way Examples – graphs, averages

Statistics

Frequency distribution – table that arranges data in a way that allows us to see how often a particular score occurs

Histogram – similar to bar graphs – always vertical & the bars always touch

Frequency Distribution/Histogram

Central Tendency

Central tendency – a number that describes something about the “average” score Used to summarize information into statistics

Measures of CT: mean, median mode

Central Tendency

Mean – an “average” score Most commonly used measure of CT

To find the mean, you add all scores and divide by the number of scores

Central Tendency

Median – the middle score The midpoint of a set of scores, so it divides the frequency distribution into two halves

Mode – the most frequent score

Central Tendency

0, 3, 4, 4, 5, 5, 6, 7, 8, 8, 8, 9, 9, 10, 10

Mean – 6.4 Median – 7 Mode - 8

Measures of Variance

Distributions show us not only the “average” score, but also how “spread out” these scores are.

Variance – provides an index of how spread out the scores of a distribution are

Measures of Variance

Range – subtract the lowest score from the highest score

Standard deviation – a measure of distance, describing an “average” distance of every score to the mean The larger the standard deviation,

the more spread out the scores are

Inferential Statistics Used to determine whether or not

the data that researchers collect supports their hypotheses, or whether their results are merely due to chance outcomes probability & chance

Ex – flipping a coin – each toss is independent of eachother

If probability that results are due to chance is less than 5%, researchers can be confident in their findings