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Exam Three
Correlations, Chi Square, Graphs, Scatterplots, Etc.
58
Mathematics
Undergraduate 1
03/19/2014

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Cards

Term
The relationship between variables
Definition
Correlation
Term
A measure of the relationship between variables
Definition
Correlation Coefficient
Term
A figure in which the individual data points are plotted in 2-dimensional space
Definition
Scatterplot
Term
Variable from which a prediction is made
Definition
Predictor Variable
Term
Variable to be predicted
Definition
Criterion Variable
Term
The predictor variable is represented on what axis?
Definition
X axis
Term
The criterion variable is represented on what axis?
Definition
Y Axis
Term
Correlation Coefficients range from what numbers?
Definition
-1 to 1
Term
When the points cluster very closely together, what line can be drawn?
Definition
Line of "best fit"
Term
If there is no relationship between the variables, what is the correlation coefficient?
Definition
0.0
Term
If the points cluster close to a line of best fit that has a postive slope, what is the correlation?
Definition
+1.00
Term
If the points cluster close to a line of best fit that has a negative slope, what is the correlation?
Definition
-1.00
Term
The closer a correlation is to -1 or +1, is the relationship weak or strong?
Definition
Strong
Term
What does the sign of the correlation coefficient mean?
Definition
The direction of the relationship
Term
What are the directions the relationship can go?
Definition

Positive; up

Negative; down

Zero; no movement

Term
Situation that is best represented by something other than a straight line
Definition
Curvilinear relationship
Term
Situation in which best-fitting line is straight
Definition
Linear relationship
Term
If a relationship isn't curvilinear or linear, what is it?
Definition
Non-linear relationship
Term

Is the relationship weak, moderate, or strong?

 

0.00, -0.20

Definition
Weak
Term

Is the relationship weak, moderate, or strong?

 

-0.50, +0.6

Definition
Moderate
Term

Is the relationship weak, moderate, or strong?

 

+0.85, -1.00

Definition
Strong
Term
A statistic representing the degree to which two variables vary together
Definition
Covariance
Term
If high scores on one variable tend to be paired with high scores on the other, the covariance will be _____ and _______
Definition
large, positive
Term
If high scores on one variable tend to be paired with low scores on the other, the covariance will be _____ and _______
Definition
large, negative
Term
If high scores on one variable tend to be paired equally with high and low scores on the other, the covariance will be ________
Definition
Near 0
Term

In cases where the range over which X and Y varies is artificially limited, what occurs?

 

What aspect of "factors that affect the correlation" is this?

Definition
r is reduced
Term

What are the 3 things that affect the correlation?

 

 

Definition

Range restrictions

Nonlinearity of the relationship

Heterogenous subsamples

Term

Restricting the range of X will increase r only when the restriction results in eliminating some curvilinear relationship.

 

What aspect of "factors that affect the correlation" is this?

Definition
Nonlinearity of the relationship
Term

Data in which the sample of observations could be subdivided into two distinct sets on the basis of some other variable.

 

What aspect of "factors that affect the correlation" is this?

Definition
Heterogenous subsamples
Term
Does correlation imply causation?
Definition
No!
Term
It has been shown that there is a positive relationship between watching TV and aggression and children. Watching TV does not cause children to be aggressive. What does this illustrate?
Definition
Correlation does not imply causation
Term
What is correlation used mainly as?
Definition
A predictor
Term
What is the regression also known as?
Definition
Line of best fit!
Term
Prediction of one variable from knowledge of one or more other variables
Definition
Regression
Term

In regression:

 

What does b stand for?

Definition
Slope of the regression line
Term

In regression:

 

What does a stand for?

Definition
the y axis intercept (when x=0)
Term
Coefficient of determination is denoted by what?
Definition
r2
Term
Meaures the proportion of variance in one variable due to the relationship with the other variable
Definition
Coefficient of determination
Term
A statistical test often used for analyzing categorical data
Definition
Chi Square
Term
Relationships between measurement variables are determined by what?
Definition
Correlation
Term
A test for comparing the observed frequencies with the expected frequencies to see if there is a significant preference
Definition
Chi squre goodness of fit
Term
What kind of graph would be good for showing a goodness of fit test?
Definition
Pie chart
Term
The number of persons in the sample who are classified in a particular category
Definition
Observed frequencies (O)
Term
The frequency values predicted for a particular category
Definition
Expected frequencies (E)
Term
Is there a statistical preference? Which test is this?
Definition
Chi squre goodness of fit
Term
Is there a relationship? What test is this?
Definition
Chi square test for independence
Term
Goal of test is to test whether there is a relationship between variables; data will often be presented in a contingency table
Definition
Chi square test for independence
Term
A 2 dimensional table in which each observation is classified on the 2 variables simultaneously
Definition
Contingency table
Term
If the calculated value exceeds the critical value, is there a relationship?
Definition
Yes
Term
If the calculated value does not exceed the critical value, is there a relationship?
Definition
No
Term
Well designed statistical pictures should what? (4 things, 1 additional)
Definition

1. Title of the picture

2. What each of the axes, bars, pie segments denotes

3. The scale of each axis, including starting points

4. A source

 

*Data should clearly stand out from the background

**There should be as little chart junk as possible

Term
Useful when one categorical variable is measured. Demonstrates what percentage of the whole falls into each category. Good for the "goodness of fit" test
Definition
Pie charts
Term
Shows percentages or frequencies in various categories. Useful to represent 2 or more categorical variables. Good for the "test for independence"
Definition
Bar graphs
Term
Similar to a bar graph except that it uses pictures related to the topic of the graph
Definition
Pictogram
Term
Graph that makes it easy to see upward/downward trends
Definition
Line graph
Term
Often used in correlation studies. Displays the relationshio between 2 measurement variables. Each mark represents someone's score. Helps us to determine the strength of the relationship between 2 variables.
Definition
Scatterplot
Term
Common problems in plots, graphs, and pictures
Definition

1. No labeling on one or more axes

2. Not starting at 0 as a way to exaggerate trends

3. Changes in labeling on one or more axes "slinky"

4. Misleading units of measurement

5. Using poor information

Term
As soon as you are presented with 2 variables, what kind of test is it?
Definition
Test for interdependence
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