Download 139 chapter 2 ppt fall 2013

The Psychology of the Person
Chapter 2 Research
Naomi Wagner, Ph.D
Lecture Outlines
Based on Burger, 8th edition
The Hypothesis-Testing Approach
Research begins with a theory, which is a
general statement about the possible
relationship between variable (explaining)
Theories differ in the range of events or
behaviors they attempt to explain
A good theory is parsimonious- uses as
few variables as possible, and usefullends itself to research.
Theories and Hypotheses
A hypothesis is a specific prediction that is
logically derived from the theory, and lends itself
to be tested in an experiment
The theory itself is never tested directly and
cannot be proven or unproven
It can be supported by research
A good research progresses fro theory, to
hypothesis (prediction) to experiment.
The experimental variables: The Independent
variable- supposed to have an impact on the
dependent variable
The Experiment
A procedure that enables us to identify cause-and effect
relationships
We manipulate the Independent Variable (IV) to assess
its influence on the Dependent Variable (DV)
To Manipulate the IV means to create different levels of
it, and assign people to be exposed to the levels
For example: If we want to assess the impact of sleep
deprivation on concentration, we will create different
levels of sleep- to see whether those who sleep more
are able to concentrate better than those who sleep less
(note issue of random assignment)
An Example
Theory: a connection between sleep and
the ability to focus in the classroom
Hypothesis: Those who sleep more are
better able to focus
The Independent variable: The amount of
sleep
The dependent variable: the ability to
focus
The Experimental Variables
We manipulate the IV by forming different levels
of it, for example, we assign participants into
sleep groups
8 hours sleep
5 hours sleep
3 hours sleep
0 hours sleep
We want to see whether those who sleep more
were better able to focus (work on a reading
task) than those who sle
How can we eliminate the impact of other factors
on the ability to focus ?
There might be other factors beside sleep
that may affect the ability to focus- for
example, someone is sick, does not speak
the language, has just now got bad news
Random assignment of participants into
the various experimental groups (e.g.
sleeping 8 hours, 5 hours, 3 hours etc)
eliminates any pre-existing differences
among the participants
Random Assignment
It sin a procedure by which each person has the
same likelihood to be assigned to any of the
experimental groups (8, 5, hours of sleep etc)
It can be done by pulling names out of a hat …
but we use tables of random numbers
When using manipulated independent variables
we assign participants at random into the
experimental groups.
Only by doing this we can say that it was the IV
(sleep) that affected concentration and not any
other variable
Non-Manipulated Independent Variables
In many situations we are not able to
randomly assign participants into groups
The groups already exist
For example: The impact of divorce of
children’s academic performance
In such cases we cannot determine
cause-and-effect relationships
The results are presented as correlations
Prediction vs. Hindsight
In research we make predictions and then
collect the data and interpret the findings
Generating a hypothesis after the result
are known (Hindsight”) is not regarded as
scientific
Replication is needed to examine
participants populations different from the
one used in the original research.
A Correlational Study
A correlation is a procedure that tells us to
what extent two variables vary togetherthat is- change in one variable is
associated with change in another variable
A correlation does not identify causeand-effect relationships
A correlation is described along its
magnitude, from -1 to 1, and directionpositive, negative, or no correlation.
Statistical Significance
A procedure that tells us the extent to which a
result in an experiment reflects real differences
among the groups, or chance fluctuations
The Statistical Significance is expressed is terms
of probability- e.g. result that is found to be
significant at the 5% tells us that there is 95%
probability that the result reflects true differences
among the subjects, and not random factors
The Case Study
This is the oldest form of study
It involves studying one person in depth,
often along time
It is useful when there is a rare case that
otherwise is difficult to study
It is also useful to show the results of
therapy
It may also be subject to bias
May be difficult to generalize to others
Psychological Assessment
Personality tests need to possess psychometric
qualities:
Reliability: the extent to which the results of the
test show consistency along time
One form of assessing reliability is “test-retest” –
administering the test to the same person at two
different points in time
Reliability also can be assessed as “internal
consistency”- the extent to which the items of the
test correlate with the overall score
Validity
The extent to which the test measures what is
claims to measure
In developing anew test, validity needs to be
demonstrated
It is easier to demonstrate validity for some
types of tests- a test (such as the SAT) to predict
how well students will do in college needs to
have predictive validity
Those who score high on the SAT were found to
have higher GPA in college
Validity (cont-d)
Often is psychology we want to measure
hypothetical constructs (such as
intelligence), and look for Construct
Validity
The following methods are used to assess
construct validity: Face Validity, Congruent
Validity, Discriminant Validity, Behavioral
Validation.
Face Validity
We judge face validity by looking at the
test items
We say that “on the face of it” the tests
measures the constructs
For example, test to measure social
anxiety will have items such as “Do you
feel nervous interacting with others?”
Some hypothetical constructs do not lend
themselves to obvious questions.
Congruent Validity
We compare the scores obtained on a new test
to scores of the same people on an “old” test in
the area
For example, when the new intelligence test (IQ)
was introduced by David Wechsler in 1939, its
validity was assessed by having people take the
new test, and the old IQ test (Stanford-Binet) to
see whether similar scores will be obtained
The extent to which scores from the test
correlate with other measures of the same
construct
Discriminant Validity
The extent to which a test score does NOT
correlate with the scores of another test that is
unrelated to it.
Example: When a researcher designs a
creativity test it is important to show that the test
measures creativity instead of something
different.
Both tests are given to a group of people and the
expectation is that correlations between the
scores on the two tests in the people will be low.
Behavioral Validation
The researcher gives the test, and then
observes the behavior of interest in real
life
For example- give a test of Stage Fright
and then observe actors just before they
go on stage to perform.
This is very relevant, as we often give a
test in order to predict behavior.