Statistics
Statistics#
Statistics are numbers that summarise raw facts and figures in a meaningful way.
Use statistics to analyse data and draw conclusions.
Why?#
- Make objective decisions
- Convey meaning
- Make accurate predictions
Statistics are based on facts, but they can be misleading
Visualising Data#
Pie Chart#
- Divide your data into groups whose frequency, when combined, comes to 100% of the total They show proportions Useful if you want to compare basic proportions Less useful* if all the slices have a similar size
Bar Chart#
- Let you compare relative sizes with the advantage of allowing a greater degree of precision Ideal for when categories are roughly the same size Horizontal or vertical bar graphs can be used* Horizontal charts are better for long field names
The golden rule for showing charts with percentages is to indicate frequencies, either on the chart or next to it.
Otherwise, one percentage taken from a few respondents can be compared with another percentage from many respondents.
What you sometimes need is to show both percentages and frequencies.
Split-category Chart#
For each genre, you can split responses into people satisfied and dissatisfied.
- Useful for comparing frequencies, but difficult for seeing proportions and percentages
Segmented Bar Chart#
Similar to split-category charts, but both satisfied and dissatisfied are shown in a single bar.
Categories vs Numbers#
Categorical, or qualitative, data is split into categories that describe qualities or characteristics.
Eg. genre, breed or type.
Numerical, or quantitative, data deals with numbers, measurements and counts. It describes quantities.
Eg. weight, length or time.
Histogram#
Numeric data allows us to display ranges of scores as a continuous scale on an axis.
Histograms are like bar charts but the area of each bar is proportional to frequency and there are no gaps between bars.