Download Research and Statistics in Psychology

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» Does sleeping less than seven hours a day
reduce how long you will live?
» Do violent video games make people more
aggressive?
» Can you make better decisions by not
deliberating about them?
» Can women judge men’s testosterone levels in
just one glance?
» Do IQ scores predict how long people will live?
» How should we go about investigating
questions like these?
» How do we find answers to our questions about
behavior that are accurate and trustworthy?
» Remember that psychology is empirical.
» Psychologists are committed to addressing
questions about behavior through formal,
systematic observation.
» This commitment to the empirical method is
what makes psychology a scientific endeavor.
Step One: Formulate a Testable Hypothesis
» A hypothesis is a tentative statement about the
relationship between two or more variables.
» To be testable, hypotheses must be formulated
precisely; the variables under study must be clearly
defined.
» Researchers achieve clear formulations by providing
operational definitions of the relevant variables.
» Operational definitions describe the actions or
procedures used to measure or control a variable.
» These operational definitions are essential for the
replication (repeating) of concluded observations.
» By replicating research, scientist are able to further
prove or potentially disprove previous research
results.
» Step Two: Select Research Method and Design the Study
» The 2nd step is to figure out how to put the hypothesis
to an empirical test.
» Method chosen depends in large degree on the nature
of the question under study.
» These various methods (experiments, case studies,
surveys, naturalistic observations, etc.) have their
advantages and disadvantages.
» Researchers must weigh pros and cons of each.
» Next, researchers must choose the participants for their
study.
Step Three: Collect the Data
Step Four: Analyze Data and Draw Conclusions
» Observations made in a study are usually
converted into numbers (raw data) to increase
objectivity of the research.
» Researchers then use statistics (descriptive and
inferential) to analyze their data and decide
whether their hypothesis has been supported.
Step Five: Report Findings
» Publication in Academic Journal
» Studies replicated
» An experiment is a research method in which
the investigator manipulates a variable under
carefully controlled conditions and whether any
changes occur in a second variable as a result.
» The purpose of an experiment is to find out
whether changes in one variable (X) causes
changes in another variable (Y).
» To put it another way, how X affects Y. (Cause
and Effect)
» The (X) in this case would be the independent
variable (IV).
» An IV is the experimental factor being
manipulated; the variable whose effect is being
studied.
» The (Y) in this case would be the dependent
variable (DV).
» The DV is the outcome factor; the variable that
may change in response to manipulations of the
IV.
» In order to evaluate the effect of the IV on the
DV, researchers study two separate distinct
groups.
» Experimental group: subjects who are exposed
to the some version of the independent
variable.
» Control group: subjects who do not receive the
special treatment given to the experimental
group.
» Placebo effect: when participants’
expectations lead them to experience some
change even when they do not receive the IV
» Confounding variables: any variable (other
than the IV) that could affect the DV; usually
variables that cannot easily be altered
» Researcher Bias: when a researcher’s
expectations or preferences about the
outcome of a study can influence the results
obtained
» Because of inherent flaws in the experimentation process
that could influence the results, researchers incorporate
various methods to decrease the impact of those flaws.
» Control variable: any element of an experiment that MUST
NOT be changed or already be similar as these
changes/differences could affect the outcome of that
experiment (used to reduce alternative explanations)
» Random assignment: assigning participants to experimental
and control conditions by chance, minimizing the preexisting
differences between the participants
» Double-blind procedure: when both researcher and
participants are unaware (“blind”) as to which group is the
experimental and which is the control.
» One factor distinguishes descriptive research
methods from experimental research
methods.
» In descriptive research, experimenters
CANNOT manipulate the variable under study.
» These methods only permit investigators to
describe patterns of behavior and discover
links between variables.
» In naturalistic observation a researcher engages
in careful observation of behavior without
intervening directly with the subjects.
Jane Goodall conducted
research on the social
lives of chimps using
naturalistic observation.
» A case study is an in-depth investigation of an
individual subject.
Anna O.
Phineas Gage
Henry Molaison
» A survey is a technique for ascertaining the selfreported attitudes or behaviors of people.
» Surveys incorporate several steps to insure
confidence in their results:
» Most importantly they use random sampling in
determining who participates in the survey.
» Random sampling (similar to random
assignment in experiments) ensure that each
member of a population has an equal chance of
inclusion.
» Whether researchers use experimental or
descriptive methods, they need some way to
make sense of their data.
» Statistics is defined as the use of mathematics
to organize, summarize and interpret numerical
data.
» Statistical analyses permit researcher to draw
conclusions based on their observations.
» Descriptive statistics
are used to organize
and summarize data.
» In summarizing numerical data, researcher want to
know what constitutes a typical or average score.
» To answer these questions they use three measures
of central tendency: median, mean and mode.
» Median: score that falls exactly in the center of a
distribution
» Mean: arithmetic average of the scores in a
distribution
» Mode: the most frequent score in a distribution
» In general, the mean is the most useful measure of
central tendency.
» However the mean is sensitive to extreme scores in a
distribution, which can sometimes make the mean
misleading. (Term defined as “skewed distribution”)
» In describing a set of data, it is
often useful to have some estimate
of the variability among the scores.
» Variability refers to how much the
scores in a set vary from one
another and from the mean.
» The standard deviation is an index
of the amount of variability in a set
of data.
» When variability is great, so too
will be the standard deviation.
» When variability is low, so too will
be the standard deviation.
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» A correlation exists when two variables are
related to each other.
» Researchers often want to quantify the strength
of an association between two variables, so
they depend on a descriptive statistic called the
correlational coefficient.
» The correlational coefficient is a numerical
index of the degree of relationship between
two variables.
Indicates strength
of relationship
(0.00 to 1.00)
Correlation
coefficient
r = + 0.37
Indicates direction
of relationship
(positive or negative)
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A correlational coefficient indicates both:
(1) the direction of the relationship
(2) and how strongly the two variables are related.
A positive (+) correlation indicates that the two
variables co-vary in the same direction.
» Up and Up; Down and Down.
» A negative (-) correlation indicates that the two
variables co-vary in the opposite direction.
» One up and one down.
»
»
»
»
» The size of the coefficient indicates the strength
of an association between two variables.
» The coefficient can vary between -1.0 and +1.0.
» A -1.0 indicates a perfect (one-to-one) negative
correlation.
» A +1.0 indicates a perfect (one-to-one) positive
correlation.
» A coefficient of zero (0) indicates no relationship
exists at all.
THE MERE FACT THAT TWO
VARIABLES ARE CORRELATED
DOES NOT MEAN THAT THERE
ALSO EXISTS A CAUSE AND
EFFECT RELATIONSHIP.
» A scatterplot is a graphed cluster of dots, each
of which represents the values of two variables.
» The slope of the points suggests the direction of
the relationship (positive or negative).
» The amount of “scatter” suggests the strength
of the correlation.
Perfect positive
correlation (+1.00)
Perfect negative
correlation (-1.00)
No relationship (0.00)
The Scatterplot below shows the relationship
between height and temperament in people. There
is a moderate positive correlation of +0.63.
» After researchers have summarized their data
with descriptive statistics, they still need to
decide whether their data support their
hypotheses.
» Inferential statistics are used to interpret data
and draw conclusions.
» Working with the laws of probability, researchers
use inferential statistics to evaluate the possibility
that their results might be due to the fluctuations
of chance.
» When statistical calculations (ones you don’t
have to worry about for this class) indicate that
research results are not likely due to chance,
the results are said to be statistically significant.
» Statistical significance is said to exist when the
probability that the observed findings are to
due chance is very low (usually about 5%
chance).