ISDS ch 3
Terms
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- mean value
- the expected value of the random variable, x. it is a weighted average in which the possible values of x are weighted according to their probablilites of occurance
- mode
- the value that occurs with the greatest frequency in a set of data
- median
- a value that has just as many observations that are higher as it does observations that are lower. it is the second quartile
- skewness
- the condition in which a distribution tails off to either the left or the right, exhibiting a lack of symmetry
- positively skewed
-
right skewed data
mean>Q2 - negatively skewed
-
left skewed data
mean<Q2 - symmetrically skewed
- mean = Q2
- range
- the difference between the highest and lowest values in a set of data
- variance
- a measure of dispersion based on the squared differences between observed values and the mean
- standard deviation
- a measure of dispersion, calculated as the positive square root of the variance
- empirical rule
- for distributions that are bell-shaped and symmetrical, about 68% of the observations will fall within 1 standard deviation of the mean, with about 95% falling within 2 standard deviations, and practically all of the observations falling within 3 standard deviations of the mean