Poli Analysis Study Guide
Mean- computing:
Add all numbers in data set then divide by total numbers in data set
Interpreting- if one were to choose a number at random from data set, one would expect it to be the
mean. It is the “average” of all numbers
Median- computing:
It is the middle number of the data set, if even amount of numbers in data set, add two middle and
divide by 2
Interpreting: means that ½ the numbers in the data set are higher than the median, and ½ the numbers
are lower
Skewness:
Positive skew: when the mean is bigger than median
Negative skew: when the median exceeds the mean
Mode- computing/interpreting:
The mode is the most reoccurring number in the data set. It means that there are no other numbers that
occur more than the mode. If no mode, state there is no mode.
Range:
Computing- take the highest number and subtract it from the lowest number in the data set
Interpreting- the range is the amount of whole numbers that exist between the highest and lowest
number in the data set. Allows us to see the relative size of the data set. Large range=large data set
Standard Deviation- used to find the extent of which the cases in a distribution fall on or close to the
mean of the distribution
Computing: take each number in data set and subtract from the mean. Square the sum. Repeat for each
number. Take the sum of all numbers subtracted from mean and square root. Then divide by total
number of cases in the population
Interpreting:
- Relative to the size of data set
oIf 100 numbers in data set and SD of 2- small SD
oIf SD is 25- large SD
- 68% of all numbers in a data set will occur within one SD of the mean
