Reading & Interpreting Statistical Diagrams
How do I read and interpret statistical diagrams?
- Rather than present you with a list of values (raw data), questions may present information using a statistical diagram
- Such diagrams may or may not be the ones that are already familiar
- Unfamiliar diagrams will be reasonably straightforward to read and interpret
- you won't need any new skills for such diagrams
- Reading and interpreting statistical diagrams requires gathering any required information from a diagram
- this enables meaningful statistics like the mean, median, mode, range and interquartile range to be calculated
- from these, conclusions about the data can be made
- Important things to look for in diagrams include
- a key, and/or shading, that indicate what certain parts of the diagram mean
- e.g. a dual bar-chart may show year 7 data in solid shading and year 8 data in striped shading
- information given through the labels on the axes
- key words on diagrams such as frequency
- anything unusual or unexpected mentioned in words, whether they come before or after a diagram
- anomalies (outliers)
- a key, and/or shading, that indicate what certain parts of the diagram mean
- You may also be asked to comment on a given statistical diagram
- this may be to point out something that could be misleading or incorrect
- e.g. uneven gaps in axes values
- e.g. a missing key
- this may be to point out something that could be misleading or incorrect
Worked example
The dual line chart below shows the number of books loaned from a library by male and female adults each day for a week.
Work out the mean number of books loaned per day by males during this particular week.
We need the number of books from the males (red line) for each of the five days and then find their mean.
Mean number of books loaned per day by males is 12.8
Work out the median number of books loaned by women per day by females during this particular week.
We need the number of books from the females (blue line) for each of the five days.
12, 15, 12, 16, 12
To find the median, these will need to be put into ascending order, then the middle value found.
12, 12, , 15, 16
The median number of books loaned per day by females is 12
Determine whether the males or females had the greater range of books loaned per day during this particular week.
Using the lists/values from the parts a) and b) ...
The males had the greater range of books loaned per day
(5 compared to 4 so their range was 1 book higher)