Averages and range
The mean shares the total equally, the median is the middle value in order, and the mode is the most common. The range measures spread. For frequency tables, multiply each value by its frequency; for grouped data, use the class midpoints.
≈ 30 minCharts, tables and scatter diagrams
A pie chart shares in proportion to the frequencies. A two-way table splits a group by two features at once. A scatter diagram shows whether two quantities are related, and a line of best fit lets you estimate one from the other within the range of the data.
≈ 30 minCumulative frequency
Cumulative frequency is a running total. Plot it against the upper class boundaries and join the points to get an S-shaped curve. Read across at for the median, and at and for the quartiles. The interquartile range is the spread of the middle half.
≈ 30 minHistograms
In a histogram, the area of each bar shows the frequency. When classes have different widths, the height is the frequency density: frequency ÷ class width. To read a frequency back, multiply density by width.
≈ 30 minCollecting data and stem-and-leaf diagrams
Data is qualitative (words) or quantitative (numbers); numbers are discrete (counted) or continuous (measured). A fair sample represents the whole population without bias. Frequency tables and stem-and-leaf diagrams organise raw data so you can read off the median, mode and range.
≈ 25 min