Measures of dispersion Flashcards
What are measures of dispersion?
A set of data can be described in terms of how dispersed or spread out the data ites are
What is the range?
The range is the arithmetic distance between the top and bottom values in a set of data
Once you have difference you have to add 1
Why do we add an additional 1 to the range?
because the bottom number of 3 could represent a value as low as 2.5 and top number 15 could be as high as 15.5
Calculate the range of this- 3, 5, 8, 8, 9, 10, 12, 12, 13, 15?
range 13
Strengths of the range?
identify the spread out of data is accounts for end values of data set
Limitations of the range?
-If affected by extreme values as values are at highest and lowest end of set are used
-Meaning it may not actually reflect data
-Fails to take into account distribution of numbers meaning it doesn’t indicate weather most numbers are closely grouped or evanly groupes
What is standard deviation?
measures if the spread of the set of numbers, in effect the average distance of each number from the mean
What is step 1 of standard deviation?
Calculate the mean
What is step 2 of standard deviation?
Subtracting mean for each raw score
What is step 3 of standard deviation?
Square the numbers from step 2
What is step 4 of standard deviation?
Add number from step 3 together
What is step 5 of standard deviation?
Divide step 4 by amount of raw score
What is step 6 of standard deviation?
square root step 5 to get the answer
Strengths of standard deviation?
-Takes precise measures of dispersion allowing all values are taken into account mean we know weather values are closer group around means or spread out
-May hide characteristics of data, like extreme values as it indicates how far each value is rather then looking at values at end of data set
Limitations of standard deviation?
-may hide characteristics of data like extreme values as it indicates how far each value is rather then looking at values at each end of data set
