Glossary of Measures of Dispersion
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- -the easiest measure of dispersion
- Calculating Range
- Subtract lowest score from highest score
- Problem with Range
- - Highly susceptible to the influence of extremely high or low outliers
- 50th Percentile
- -The point in an ordered distribution of scores below which 50% of the scores fall
-An indicator of position
- -Points in an array that divide the scores into 4 equally sized groups
- Interquartile Range or
- -Variant of the rante that manages to avoid the problem of outliers by focusing on the middle 50% of scores
- Problem with Interquartile Range
- Fails to say anything about the positioning or values of other scores in the data set
- Semi-interquartile Range
- -Provides a general indicator of how scores vary around the median
- Semi-interquartile Range is not affected by...
- not affected by outliers
- Calculating semi-interquartile range
- Divide the interquartile range by 2
- -Distance between a score and the mean
- Variance is also known as...
- The Mean Square
- -The arithmetic average of the squared deviation
- Standard Deviation
- -Square root of the variance that tells us how far the average score in a distribution varies from the mean
- If the scores in a distribution are spread out then....
If the scores are compacted then...
- 1 - If spread out, it is a LARGE standard deviation
2 - If compact, a small standard deviation
- What does standard deviation allows us to compare?
- Standard deviation allows us to compare the variability that exists among groups or samples.
- Best level(s) of measurement for a standard deviation
- Ratio or Interval
- Boxplot is also known as a...
- Box-and-Whisker diagram
- - A graphical means of summarizing how th evalues in a data set are dispersed
- 5 number summary
- - A boxplot that depicts 5 important indicators of dispersion
- The 5-number summary indicators
- 1. Maximum
2. 3rd Quartile
4. 1st Quartile
- Extreme Scores
- -Values that fall a distance that's more than 3 times the value of the interquartile range beyond the hings of the central box
- Index of Dispersion
- Provides a ratio of the number of unique pairs that can be created out of the observed scores to the total number of unique pairs possible
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