Chapter 7 – Summarizing and Displaying Measurement Data
Mean – average
Median – the middle number (or average of the two middle numbers)
Mode – the most common number
Outlier – one or two numbers that are far from the other numbers
Variability tells us how spread out the results are. We find the minimum and the maximum and
determine the range.
Shape shows a picture of the data. A stemplot is an easy way to organize a list of numbers. They are
sometimes called stem and leaf plots or stem and leaf diagrams. First we make the stems. They are the
first numbers of each number. The leaves are the second number of each number. You can repeat the
numbers used for stems to give the picture more meaning. The shape helps identify outliers, the centre.
Sometimes there are no obvious outliers. A histogram is a bar graph. We draw bars for the number of
numbers within a range. They are drawn equal to the proportion that they account for. The sum of the
bars must reach 100%. A symmetric data set is one that you can draw a line right through and have
mirror images on either side. A bell-shaped data set is a very common symmetric data set. If there is one
peak in a histogram or stemplot it is called unimodal. If there are two peaks it is called bimodal. A
skewed data set is unimodal, but is not bell-shaped. It is skewed to the right if the higher values are
more spread out than the lower values. If it is skewed to the left the lower values are more spread out.
A skew is the direction of the unusual values. A five number summary is a summary of data using five
numbers. Quartiles are the medians of the two halves of the ordered list. The lower quartile is a quarter
up from the bottom and the upper quartile is a quarter down from the top. We can find these by finding
the median of each half. A visually appealing way to show the five number summary is a boxpl