Statistics Review: Mean, mode, median, range, quartiles

Statistics is the study of data: how to collect, summarize and present it.  We commonly use some parameters to support our statistic studies, these are the following I sum up here for you:



The statistical mean is commonly called the average:

To find the mean of a group of numbers:

• Add the numbers together
• Divide by how many numbers were added together

Mean 1
Mean 2

The statistical mode is the number that occurs most frequently in a set of numbers.

To find the mode of a group of numbers:

• Arrange the numbers in order by size.
• Determine the number of instances of each numerical value.
• The numerical value that has the most instances is the mode.
• There may be more than one mode when two or more numbers have an equal number of instances and this is also the maximum instances
• A mode does not exist if no number has more than one instance.

Example: The mode of 2, 4, 5, 5, 5, 7, 8, 8, 9, 12 is 5.

Mode

The statistical median is middle number of a group of numbers that have been arranged in order by size. If there is an even number of terms, the median is the mean of the two middle numbers:
To find the median of a group of numbers:

• Arrange the numbers in order by size
• If there is an odd number of terms, the median is the center term.
• If there is an even number of terms, add the two middle terms and divide by 2.

Median 1
Median 2

The statistical range is the difference between the lowest and highest valued numbers in a set of numbers.

To find the range of a group of numbers:

• Arrange the numbers in order by size
• Subtract the smallest number from the largest number.

Range 1
Range 2

Quartiles are the values that divide a list of numbers into quarters.

• First put the list of numbers in order
• Then cut the list into four equal parts
• The Quartiles are at the "cuts"

Quartiles 1
Quartiles 2
Quartiles 3
Quartiles 4