Cheatography

# MMW Cheat Sheet by niicat

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. 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)

 Q3 = also known as UPPER QUARTILE Q1= also known as LOWER QUARTILE

### CHAPTER 6: Measures of Dispersion

 2 IMPORTANT MEASURES OF DISPERSION - variance - standard deviation