Between Relationships Variables
Linear relationships
Positive linear relationship.
Both variables increase or decrease at the same rate in the same direction. Represented as a straight line going up on a R t d t i ht li i graph
Linear Relationship Graphs
Positive Negative
Negative linear relationship
As one variable increases the other variable decreases at the same rate. Represented as a straight line going down on a graph
12 13
Relationships Between Variables
Curvilinear relationship
As one variable increases the other variable both increases and decreases over time (nonmonotonic). Represented as a curved line on a graph.
Curvilinear Relationship Graph
No Relationship between variable changes
Represented by a flat, horizontal line on a graph.
14 15
A researcher measured how much violent television children watched at home. These children were also observed for their aggressiveness on the playground. The researcher found that as the amount of violence watched on TV increased, the amount of playground aggressiveness increased. The type of relationship found was
The finding that a persons shoe size is not associated with their family income suggests what type of relationship?
A. B. C. D.
negative linear. positive linear. curvilinear. none of these
A. B. C. D.
negative linear. positive linear. curvilinear. none of these
16
17
1
Dr. Kramer found that the average number of miles driven decreases as the price of gasoline increases. This relationship can best be described as a _______ relationship.
A researcher finds that the more a song is played on the radio, the greater the liking for the song. However, she also finds that if the song is played too much, people start to dislike the song. What type of relationship does this represent?
A. B. C. D.
negative linear. positive linear. curvilinear. none of these
A. B. C. D.
negative linear. positive linear. curvilinear. none of these
18
19
Experimental vs. Nonexperimental Methods
Nonexperimental methods simply measure the variables of interest in an attempt to discover a relationship between them (if there is a correlation between them). th i l ti b t th ) Experimental methods systematically change some variables and measure the effects of these changes on other variables to assess the relationship between them.
20
Nonexperimental Methods
These methods are good for discovering if two or more variables covary. covary.
Covariation or correlation is useful for prediction (if you know the value of one variable you can predict the value of correlated i bl di t th l f l t d variable.
Examples: High SAT scores are positively correlated with success in college, seat belt use is negatively correlated with severe injury in auto accidents.
21
Nonexperimental Methods
Causality MUST NOT be inferred from correlational methods
The problem of determining the direction of cause and effect effect.
Which change came first?
Experimental Methods
Experimental methods introduce techniques of control that allow inferences of causality.
Extraneous variables are held constant and/or their effects are randomized across experimental conditions.
This solves the third variable problem.
The third-variable problem thirdDid some other variable produce the changes in the two measured variables?
One variable is systematically changed (the independent variable) while changes in the other variable (dependent variable) are measured.
This solves the cause/effect direction problem.
22 23
2
Students watched cartoons either alone or with others and then rated each cartoon on a funny scale. The independent variable was and _____ the dependent variable was ___________.
Teachers were told a childs parents were either college grads or high school dropouts. There were than asked to rate the childs academic potential. The independent variable was _____ and the dependent variable was ___________.
A. The children; p ; parents education B. The teachers; rating of education C. What teachers were told; teachers rating of child academic potential D. Academic potential of child; teachers beliefs
A. The cartoons, humor , B. The funny rating, the watching condition C. The students, the funny rating D. The watching condition, the funny rating
24
25
Dr. Sears observes that the more time a person spends in a department store, the more purchases they tend to make. The research method used in this study can best be described as
A. B. B C. D. experimental non-experimental noni t l operational independent
Experimental Methods & Causality
To infer causality we must consider the following
Temporal order (cause comes before effect) There must be covariation between variables (as one variable changes there must be a corresponding change in the other variable) Other explanations for the change must be eliminated
26
27
Which one of the following represents a critical difference between the nonexperimental and experimental methods?
A. Nonexperimental methods involve operational definitions while experimental methods do not. B. Experimental methods involve operational definitions while nonexperimental methods do not. C. Nonexperimental methods involve the manipulation of variables while experimental methods do not. D. Experimental methods involve the manipulation of variables while nonexperimental methods do not.
Determining which Research Method to Use
Requirement for experimental control can make experiments less real.
Limits the questions asked and reduces the generalization of the findings. Nonexperimental field studies are more realistic but extraneous variables are less controlled.
Ethical and practical concerns limit what can be manipulated and controlled.
28 29
3
Determining which Research Method to Use
When description and prediction are all that ...