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CHAPTER 6: Measures of Dispersion
CHAPTER 6: Measures of Dispersion
- these are statistical measures that summarize the amount of spread or variation in the distribution of values in a variable. |
- the more similar the scores are to each other, the lower the measures of dispersion will be. |
- it describes how values are spread within the distribution |
- the less similar the scores are to each other, the higher the measures of dispersion will be. |
- it also describe how similar a set of scores are to each other. |
- in general, the more spread out a distribution is, the larger the measure of dispersion will be. |
RANGE
- it is the difference between the largest and smallest number in a set of observation. |
- the range is rarely used in scientific work as it is fairly insensitive. |
- it is used mostly for quick and easy indication of variability. |
- the range can be used when you are presenting your results to people with little or no knowledge of statistics. |
- it can be used with ordinal or interval- ratio variables. |
- two diff sets of data may have same range. |
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1, 1, 1, 1, 9 vs 1, 3, 5, 7, 9 |
Range Formula:
Ungroup data |
Group Data |
Range= Highest Score - Lowest Score |
Range= Highest Class Mark - Lowest Class Mark |
INTER- QUARTILE RANGE (IQR)
- it is defined as the difference of the first and third quartile of a data set. |
- it is a measure where the "middle fifty" lies in the data set. |
- therefore, because it uses the middle 50%, it is not affected by outliers or extreme values. |
INTER- QUARTILE RANGE (IQR)
INTER- QUARTILE RANGE (IQR)
INTER- QUARTILE RANGE (IQR)
Q3 = also known as UPPER QUARTILE |
Q1= also known as LOWER QUARTILE |
INTER- QUARTILE RANGE (IQR)
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CHAPTER 6: Measures of Dispersion
2 IMPORTANT MEASURES OF DISPERSION |
- variance |
- standard deviation |
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