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14 Cards in this Set
- Front
- Back
Scatter plot |
a collection of set data points, one data point per person or object. |
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If there is a clear relationship, quantities are said to be ... |
correlated |
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Correlation is used to determine... |
if there is a relationship between two variables and, if so, the strength and directions of that relationship |
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A line that fits the data points in a scatter plot is called a ... |
regression line |
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Correlation Coefficient |
A measure that is used to describe the strength and direction of a relationship between variables whose data points lie on or near a line |
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Correlation coefficient is designated by |
r |
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Variables are _________ if they tend to increase or decrease together |
positively correlated |
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Variables are negatively correlated if |
one variable tends to decrease while the other increases
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Perfect positive correlation |
all points in the scatter plot lie precisely on the regression line that rises from the left to the right |
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Perfect negative correlation |
all points in the scatter plot lie precisely on the regression line that falls from the left to the right |
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Correlation coefficient formula |
r = n(sum of xy) - (sum of x)(sum of y) divided by square root of n(sum x squ)-(sum x) squ times square root of n(sum y squ) - (sum y)squared |
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When computing correlation coefficient by hand, organize work in 5 columns ... |
x y xy x squared y squared in graph form, bottom of graph will have: sum of x's, sum of y's, sum of xy's, sum of x squareds, sum of y squareds |
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Writing the equation of the regression line by hand |
-- y=mx + b -- m= n(sum xy) - (sum x)(sumy) divided by (n(sum x squared) - (sum x) squared -- b = sum y - m(sum x) divided by n |
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Significance level of 5% or 1% or... ex: |
determines if variable correlation is not related to the population |