Central tendency describes the middle or a typical value of the data set and is measured using the mean, median, and mode.
Variability describes how spread out the data is.
Quartiles divide a data set into four equal parts. The third quartile minus the first quartile is the range for the middle half of the data.
A box-and-whisker plot shows the distribution of data. The middle half of the data is represented by a box with a vertical line at the median. the lower first and upper fourth are represented by whiskers that extend to the smallest and largest values.
Example:
Draw a box-and-whisker plot for the table below, that summarizes a veterinaian's record for kitten litters born in a given year.
Litter Size
2
3
4
5
6
Number of Litters
1
6
8
11
1
Order the data and find the smallest value, first quartile, median, third quartile and largest value.
2 3 3 3 3 3 3 4 4 4 4 4 4
4
4 5 5 5 5 5 5 5 5 5 5 5 6
Lower half
Upper half
2 3 3 3 3 3 3 4 4 4 4 4 4
4
4 5 5 5 5 5 5 5 5 5 5 5 6
First quartile
Second quartile
Third quartile
median of lower half:3
Median:4
median of upper half:5
smallest value: 2
first quartile: 3
median: 4
third quartile: 5
largest value: 6
Draw a number line and plot above each value from step 1
Draw the box and whiskers.
Directions: Answer the following questions. Also write at least 5 examples of your own.