Statistical diagrams

Question 1

Bar charts

Answer 1

used to show frequencies for each item of data, with the height of the bar equal
to the frequency. Unlike histograms, there are gaps between the bars. Bar charts are often used
for categorical data

Question 2

Dot plot

Answer 2

similar to a bar chart but uses stacks of dots to represent frequency.

Question 3

vertical line chart

Answer 3

similar to a bar chart but uses vertical lines instead of bars. This is more
appropriate than a bar chart to show numerical data

Question 4

histogram

Answer 4

used to illustrate grouped data. The vertical axis gives frequency density (found by
dividing the frequency by the class width). The frequency for each group is proportional to the
area of the bars, and there are no gaps between the bars.

Question 5

stem-and-leaf diagram

Answer 5

used for numerical data. The stem indicates groups of data, and the
leaves give the actual data. It shows the shape of the distribution in the same way that a bar
chart, dot plot or vertical line graph does, but includes the actual raw data

Question 6

box-and-whisker diagram, or boxplot

Answer 6

summarises numerical data by showing the lowest
value, the lowest quartile, the median, the upper quartile and the highest value

Question 7

cumulative frequency curve

Answer 7

a graph illustrating numerical data. For each value, x, the total
frequency of data less than or equal to x is plotted against x. A cumulative frequency curve is
useful for estimating the values of the median, quartiles or other percentiles.