The Psychology of the PersonThe Psychology of the PersonChapter 2 Research Chapter 2 Research

Naomi Wagner, Ph.DNaomi Wagner, Ph.D

Lecture Outlines Lecture Outlines

Based on Burger, 8Based on Burger, 8thth edition edition

The Hypothesis-Testing Approach The Hypothesis-Testing Approach

Research begins with a theory, which is a Research begins with a theory, which is a general statement about the general statement about the possiblepossible relationship between variable (explaining) relationship between variable (explaining) Theories differ in the range of events or Theories differ in the range of events or behaviors they attempt to explain behaviors they attempt to explain A good theory is A good theory is parsimoniousparsimonious- uses as - uses as few variables as possible, and few variables as possible, and usefuluseful- - lends itself to research.lends itself to research.

Theories and HypothesesTheories and Hypotheses

A hypothesis is a specific prediction that is A hypothesis is a specific prediction that is logically derived from the theory, and lends itself logically derived from the theory, and lends itself to be tested in an experimentto be tested in an experimentThe theory itself is never tested directly and The theory itself is never tested directly and cannot be proven or unprovencannot be proven or unprovenIt can be supported by research It can be supported by research A good research progresses fro theory, to A good research progresses fro theory, to hypothesis (prediction) to experiment. hypothesis (prediction) to experiment. The experimental variables: The Independent The experimental variables: The Independent variable- supposed to have an impact on the variable- supposed to have an impact on the dependent variabledependent variable

The Experiment The Experiment

A procedure that enables us to identify cause-and effect A procedure that enables us to identify cause-and effect relationshipsrelationshipsWe manipulate the Independent Variable (IV) to assess We manipulate the Independent Variable (IV) to assess its influence on the Dependent Variable (DV)its influence on the Dependent Variable (DV)To Manipulate the IV means to create different levels of To Manipulate the IV means to create different levels of it, and assign people to be exposed to the levelsit, and assign people to be exposed to the levelsFor example: If we want to assess the impact of sleep For example: If we want to assess the impact of sleep deprivation on concentration, we will create different deprivation on concentration, we will create different levels of sleep- to see whether those who sleep more levels of sleep- to see whether those who sleep more are able to concentrate better than those who sleep less are able to concentrate better than those who sleep less ((note issue of random assignment) note issue of random assignment)

An Example An Example

Theory: a connection between sleep and Theory: a connection between sleep and the ability to focus in the classroomthe ability to focus in the classroom

Hypothesis: Those who sleep more are Hypothesis: Those who sleep more are better able to focus better able to focus

The Independent variable: The amount of The Independent variable: The amount of sleep sleep

The dependent variable: the ability to The dependent variable: the ability to focus focus

The Experimental VariablesThe Experimental Variables

We manipulate the IV by forming different levels We manipulate the IV by forming different levels of it, for example, we assign participants into of it, for example, we assign participants into sleep groups sleep groups 8 hours sleep8 hours sleep5 hours sleep 5 hours sleep 3 hours sleep 3 hours sleep 0 hours sleep 0 hours sleep We want to see whether those who sleep more We want to see whether those who sleep more were better able to focus (work on a reading were better able to focus (work on a reading task) than those who sle task) than those who sle

How can we eliminate the impact of other factors How can we eliminate the impact of other factors on the ability to focus ? on the ability to focus ?

There might be other factors beside sleep There might be other factors beside sleep that may affect the ability to focus- for that may affect the ability to focus- for example, someone is sick, does not speak example, someone is sick, does not speak the language, has just now got bad news the language, has just now got bad news Random assignment of participants into Random assignment of participants into the various experimental groups (e.g. the various experimental groups (e.g. sleeping 8 hours, 5 hours, 3 hours etc) sleeping 8 hours, 5 hours, 3 hours etc) eliminates any pre-existing differences eliminates any pre-existing differences among the participants among the participants

Random Assignment Random Assignment

It sin a procedure by which each person has the It sin a procedure by which each person has the same likelihood to be assigned to any of the same likelihood to be assigned to any of the experimental groups (8, 5, hours of sleep etc)experimental groups (8, 5, hours of sleep etc)It can be done by pulling names out of a hat … It can be done by pulling names out of a hat … but we use tables of random numbers but we use tables of random numbers When using manipulated independent variables When using manipulated independent variables we assign participants at random into the we assign participants at random into the experimental groups.experimental groups.Only by doing this we can say that it was the IV Only by doing this we can say that it was the IV (sleep) that affected concentration and not any (sleep) that affected concentration and not any other variable other variable

Non-Manipulated Independent VariablesNon-Manipulated Independent Variables

In many situations we are not able to In many situations we are not able to randomly assign participants into groupsrandomly assign participants into groups

The groups already existThe groups already exist

For example: The impact of divorce of For example: The impact of divorce of children’s academic performance children’s academic performance

In such cases we cannot determine In such cases we cannot determine cause-and-effect relationshipscause-and-effect relationships

The results are presented as correlationsThe results are presented as correlations

Prediction vs. HindsightPrediction vs. Hindsight

In research we make predictions and then In research we make predictions and then collect the data and interpret the findingscollect the data and interpret the findings

Generating a hypothesis after the result Generating a hypothesis after the result are known (Hindsight”) is not regarded as are known (Hindsight”) is not regarded as scientificscientific

Replication is needed to examine Replication is needed to examine participants populations different from the participants populations different from the one used in the original research. one used in the original research.

A Correlational Study A Correlational Study

A correlation is a procedure that tells us to A correlation is a procedure that tells us to what extent two variables vary together- what extent two variables vary together- that is- change in one variable is that is- change in one variable is associated with change in another variableassociated with change in another variableA correlation does not identify cause-A correlation does not identify cause-and-effect relationshipsand-effect relationshipsA correlation is described along its A correlation is described along its magnitude, from -1 to 1, and direction- magnitude, from -1 to 1, and direction- positive, negative, or no correlation. positive, negative, or no correlation.

Statistical SignificanceStatistical Significance

A procedure that tells us the extent to which a A procedure that tells us the extent to which a result in an experiment reflects real differences result in an experiment reflects real differences among the groups, or chance fluctuationsamong the groups, or chance fluctuations

The Statistical Significance is expressed is terms The Statistical Significance is expressed is terms of probability- e.g. result that is found to be of probability- e.g. result that is found to be significant at the 5% tells us that there is 95% significant at the 5% tells us that there is 95% probability that the result reflects true differences probability that the result reflects true differences among the subjects, and not random factorsamong the subjects, and not random factors

The Case Study The Case Study

This is the oldest form of study This is the oldest form of study It involves studying one person in depth, It involves studying one person in depth, often along timeoften along timeIt is useful when there is a rare case that It is useful when there is a rare case that otherwise is difficult to studyotherwise is difficult to studyIt is also useful to show the results of It is also useful to show the results of therapy therapy It may also be subject to bias It may also be subject to bias May be difficult to generalize to othersMay be difficult to generalize to others

Psychological AssessmentPsychological Assessment

Personality tests need to possess psychometric Personality tests need to possess psychometric qualities: qualities: Reliability: the extent to which the results of the Reliability: the extent to which the results of the test show consistency along timetest show consistency along timeOne form of assessing reliability is “test-retest” – One form of assessing reliability is “test-retest” – administering the test to the same person at two administering the test to the same person at two different points in timedifferent points in timeReliability also can be assessed as “internal Reliability also can be assessed as “internal consistency”- the extent to which the items of consistency”- the extent to which the items of the test correlate with the overall score the test correlate with the overall score

ValidityValidity

The extent to which the test measures what is The extent to which the test measures what is claims to measureclaims to measureIn developing anew test, validity needs to be In developing anew test, validity needs to be demonstrated demonstrated It is easier to demonstrate validity for some It is easier to demonstrate validity for some types of tests- a test (such as the SAT) to predict types of tests- a test (such as the SAT) to predict how well students will do in college needs to how well students will do in college needs to have predictive validity have predictive validity Those who score high on the SAT were found to Those who score high on the SAT were found to have higher GPA in college have higher GPA in college

Validity (cont-d) Validity (cont-d)

Often is psychology we want to measure Often is psychology we want to measure hypothetical constructs hypothetical constructs (such as (such as intelligence), and look for Cintelligence), and look for Construct onstruct Validity Validity

The following methods are used to assess The following methods are used to assess construct validity: Face Validity, Congruent construct validity: Face Validity, Congruent Validity, Discriminant Validity, Behavioral Validity, Discriminant Validity, Behavioral Validation. Validation.

Face Validity Face Validity

We judge face validity by looking at the We judge face validity by looking at the test itemstest itemsWe say that “on the face of it” the tests We say that “on the face of it” the tests measures the constructs measures the constructs For example, test to measure social For example, test to measure social anxiety will have items such as “Do you anxiety will have items such as “Do you feel nervous interacting with others?” feel nervous interacting with others?” Some hypothetical constructs do not lend Some hypothetical constructs do not lend themselves to obvious questions. themselves to obvious questions.

Congruent ValidityCongruent Validity

We compare the scores obtained on a new test We compare the scores obtained on a new test to scores of the same people on an “old” test in to scores of the same people on an “old” test in the areathe areaFor example, when the new intelligence test (IQ) For example, when the new intelligence test (IQ) was introduced by David Wechsler in 1939, its was introduced by David Wechsler in 1939, its validity was assessed by having people take the validity was assessed by having people take the new test, and the old IQ test (Stanford-Binet) to new test, and the old IQ test (Stanford-Binet) to see whether similar scores will be obtained see whether similar scores will be obtained The extent to which scores from the test The extent to which scores from the test correlate with other measures of the same correlate with other measures of the same construct construct

Discriminant Validity Discriminant Validity

The extent to which a test score does NOT The extent to which a test score does NOT correlate with the scores of another test that is correlate with the scores of another test that is unrelated to it. unrelated to it. Example: When a researcher designs a Example: When a researcher designs a creativity test it is important to show that the test creativity test it is important to show that the test measures creativity instead of something measures creativity instead of something different. different. Both tests are given to a group of people and Both tests are given to a group of people and the expectation is that correlations between the the expectation is that correlations between the scores on the two tests in the people will be low. scores on the two tests in the people will be low.

Behavioral Validation Behavioral Validation

The researcher gives the test, and then The researcher gives the test, and then observes the behavior of interest in real observes the behavior of interest in real lifelife

For example- give a test of Stage Fright For example- give a test of Stage Fright and then observe actors just before they and then observe actors just before they go on stage to perform. go on stage to perform.

This is very relevant, as we often give a This is very relevant, as we often give a test in order to predict behavior. test in order to predict behavior.