Transcript Probabilities and Correlations

Probabilities and Relationships
What is probability?
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Probability statements provide descriptions about the
relative power or the ability to repeat something.
Sometimes these statements include chance. How much
chance are you willing to accept?
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Coin flipping
Gambling
Life’s oddities and chance
Measures of Relationship
Relationships among two variables
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Knowledge of relationships can assist decision making
about training and performance, e.g., when wanting to
train for the long jump a performer might focus on
creating gastrocnemius strength.
Knowledge of relationships can also help improve the
efficiency of a test by determined the critical number of
items contained in it.
Graphing of Scores
Student
Statistics
Score
Measurement
Score
ABE
92
94
BARB
85
89
CAT
71
78
DEB
91
90
EM
94
95
FRAN
75
78
GER
82
80
Graphing Technique
Student
Statistics
Score
Measurement
Score
ABE
92
94
BARB
85
89
CAT
71
78
DEB
91
90
EM
94
95
FRAN
75
78
GER
82
80
M
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STATISTICS
Scatter plots representing the relationship
of two variables
From: Rothstein, A. L. (1985). Research Design & Statistics for Physical Education. PrenticeHall, Inc.: Englewood Cliffs, NJ.
From: http://en.wikipedia.org/wiki/Scatter_plot
Mathematical Technique
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Correlations range from a -1.00 to a +1.00
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Perfect positive correlation (+1.00)
Perfect negative correlation (-1.00)
A correlation value (statistic) closer to 1.00 or
-1.00 represents more related values than values closer
to 0.
Two Types of Correlations
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Pearson Correlation
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Assumes interval or ratio (continuous) scores
Spearman Correlation
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Assumes ordinal (rank) scores
Factors Affecting Measures of Relationship
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Scores that have low reliability
Range of the scores
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Relationships shrink for more homogeneous scores