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Correlation
The way 2 factors vary together and how well one predicts the other
Positive Correlation- direct relationship where factors increase or decrease together
Negative Correlation – Inverse relationship where one factor goes up while one goes down
Continued…
Illusory Correlation
-perceiving correlation when none exists
-we notice random coincidences as not random, rather as correlated
Statistical Reasoning
Mode – the most frequently occurring score in a distribution
Mean – the arithmetic average of a distribution
Median – the middle score in a distribution
Measures of Variation
Range – the difference between the highest and lowest scores in a distribution
Standard Deviation – A computed measure of how much scores vary around the mean score
Statistical Significance – A statistical statement of how likely it is that an obtained result occurred by chance
68-95-99.7 Rule
In practice, one often assumes that the data are from an approximately normally distributed population.
If that assumption is justified, then about:– 68% of the values are within 1 standard deviation of
the mean
– about 95% of the values are within two standard deviations
– and about 99.7% lie within 3 standard deviations.
Skew
A distribution is skewed if one of its tails is longer than the other. – Positive Skew - long tail in the positive direction.
– Negative Skew - long tail in the negative direction.
– No Skew – symmetric, normal distribution.
Distributions with positive skew are sometimes called "skewed to the right" whereas distributions with negative skew are called "skewed to the left."