Module 3
Correlation coefficients can range from
-1 to 1
What is an experiment?
A method of research that manipulates an independent variable to measure its effect on a dependent variable. It is a research strategy that tests behavioral effects on one or more variables.
Professor Andrews found that as the number of days absent increases, students grades decrease. Professor Andrews has found:
A negative correlation between days absent and grades.
What does scatter plot do?
It provides a visual representation of the relationship
What does a double-blind procedure do?
It reduces possible experimenter bias (from researcher's perspective) and controls a possible placebo effect (from participant's perspective).
What does "no correlation" mean?
Knowing one variable tells you nothing about the other variable
Professor Rossi wants to represent the data she collected on age and income as single points on a chart. She can accomplish this using a:
Scatterplot
Describe the steps of the scientific method
1) Observe an interesting behavior 2) Form initial theory 3) Construct hypothesis from the theory 4) Test hypothesis by manipulating independent variable(s) and measuring dependent variable(s) 5) If results don't support hypothesis -> revise theory -> construct hypothesis, etc. 6) If results support hypothesis -> try to replicate results 7) If results can be replicated -> theory is established 8) If results cannot be replicated -> theory is rejected 9) form a new theory -> construct hypothesis, etc.
Michael notices that the plants in his garden that are in the shade most of the day are smaller than the ones that are in the sun. What can Michael conclude about the relationship between sunlight and plant growth?
A positive correlation between amount of sunlight and plant growth.
Professor McManus shows a scatterplot of data that show that grades increase as the number of hours spent studying increases. Professor McManus has shown that:
A positive correlation between studying and grades.
What is a double-blind procedure?
A research technique that keeps participants and researchers unaware of which condition each participant has been assigned to in an experiment.
What is the scientific method?
A self-correcting process for asking questions and evaluating ideas through observation and analysic
What is a hypothesis?
A testable prediction, typically derived from a theory
What is a theory?
An explanation using an integrated set of principles that organizes and predicts observations.
If a researcher wants to know the relationship between two variables that they cannot manipulate in laboratory, such as the average temperature and the amount of carbon emitted in a given year, the researcher can:
Compute a correlation
Professor Mendez wants to know how people develop stereotypes. In order to understand how, Professor Mendez will have to:
Conduct an experiment.
A correlation allows a researcher to:
Describe the relationship between two variables.
What is the emperical approach to scientific study?
Directly observing what we want to study
Researchers conduct ____________________ when they want to establish causation.
Experiments
(T/F) A correlation between two variables indicates that one variable influences the other variable.
False; it does not. In other words, correlation does not imply causation.
What is a Correlational research? What type of conclusions do they get?
In a correlational research, research measures two or more factors and tries to discover if these factors are related. They get Prediction, predicting when behavior will occur, under which condition.
What is random assignment?
In an experiment, assigning participants to experimental and control conditions by chance, to minimize preexisting differences between the different groups
What is placebo?
In an experiment, false or ineffective treatment administered as if it were the real treatment
What is an independent variable?
In an experiment, the experimental factor that is being manipulated, and whose effect is being studied
What is an experimental research? what type of conclusions do they get?
In an experimental research, researchers change the setting of one factor in a situation to see how it changes the participants behaviors. They get Causation, allowing them to say that one factor actually changes the value of another factor; an experiment is the only way to be able to draw this type of conclusion.
What is an observational research? what type of conclusions do they get?
In observational study, researcher records ongoing behavior in a natural or laboratory setting. They get Description from observational researches; describing an actual behavior.
A positive correlation:
Indicates that as one variable increases, the other variable increases.
An upward sloping scatterplot indicates:
Positive correlation
Professor Gliserman is studying the effect of alcohol on response time. Professor Gliserman will likely find _________________ between the two variables.
Positive correlation
A _________________ shows two variables combined as individual points on a graph.
Scatterplot
What is correlation?
Statistical measure of the strength of the relationship between two variables- that is, the extent to which scores on the two variables go up or down together
What is control condition? what is the purpose of control condition?
The "treatment-absent" condition in an experiment (used as a comparison for evaluating the effect of the treatment)
What is an experimental condition?
The "treatment-present" condition in an experiment
What is a dependent variable?
The outcome factor in an experiment that may change in response to manipulations of the independent variable
What is measurement?
The process of objectively recording an observation, usually as a number in order to share the knowledge among scientists
(T/F) Experiments explore cause and effect relationships by manipulating an independent variable, measuring dependent variable, and controlling all other variables.
True
scatter plots show
Two scores represented as individual points on the graph.
What does "Negative correlated" mean?
Two variables are negatively correlated if they vary systematically in the opposite direction, with one increasing while the other decreases.
What does "positive correlated" mean?
Two variables are positively correlated if they systematically vary in the same direction, increasing or decreasing together
Dr. Velasquez found a correlation of r=0.02 in a recent study. The two variables in his study are:
Uncorrelated.
If high values in one variable are associated with both high and low values of the other variables, the variables are:
Uncorrelated.
Professor Hartwick finds that people who tend to score low on one variable tend to score low on another variable. Professor Hartwick has found:
a Positive correlation.
What is a correlation coefficient?
a statistic (a number) which indicates the strength of the association between the two variables; it can take values ranging from +1.0 (the strongest possible positive correlation) through 0.0 (no correlation at all) to -1.0 (the strongest negative correlation)
Which of the following correlation coefficients may represent a strong positive correlation? a) 0.80 b) -0.80 c) 1.20 d) 0.10
a) 0.80
Which of the following is correct representation of a strong negative correlation? a) r=-0.82 b) c=-0.82 c) r=-0.22 d) c=-0.22
a) r=-0.82
What does correlation analysis do?
allows us to test the relationship between the two variables
Which of the following correlation coefficients may represents the weakest negative correlation? a) -0.80 b) -0.20 c) -1.01 d) 0.10
b) -0.20
Professor Zhang found a correlation of -0.76. What data could this correlation represent? a) The relationship between depressive symptoms and age. b) The relationship between antidepressant dose and depressive symptoms. c) The relationship between month of year and anxiety. d) The relationship between depressive symptoms and gender.
b) The relationship between antidepressant dose and depressive symptoms.
Which of the following correlation coefficients would you expect to see between months of birth (1 through 12) and scores on an intelligence test? a) 0.72 b) 0.62 c) -0.02 d) 0.52
c) -0.02
A downward sloping scatterplot indicates:
negative correlation
What is the symbol used for correlation coefficient?
r
