# cueFlash

## Glossary of Measures of Dispersion

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Range
-the easiest measure of dispersion
Calculating Range
Subtract lowest score from highest score
(38-18=?)
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
Quartiles
-definition-
-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
-definition-
-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
Deviation
-definition-
-Distance between a score and the mean
Variance is also known as...
The Mean Square
Variance
-definition-
-The arithmetic average of the squared deviation
Standard Deviation
-definition-
-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
Boxplot
-definiton-
- A graphical means of summarizing how th evalues in a data set are dispersed
5 number summary
-definition-
- A boxplot that depicts 5 important indicators of dispersion
The 5-number summary indicators
1. Maximum
2. 3rd Quartile
3. Median
4. 1st Quartile
5. minimum
Extreme Scores
-definition-
-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
-definition-
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