Stem-and-leaf diagrams and time series
Write data in a stem-and-leaf diagram and read it, then draw a time series as a line graph and smooth it with a moving average.
- Iran: grade 10
- Afghanistan: grade 10
- Russia: grade 7
Guide
In a stem-and-leaf diagram diagram each number is split into a stem (the tens) and a leaf (the ones). The stems go down the left, and the leaves of each stem are written in order along its row. A key explains it: 2|4 means 24. The diagram keeps every value, and turned sideways it looks like a histogram.
A time series is a set of values measured at regular times (every day, every week). It is drawn as a line graph with time on the horizontal axis, and the points are joined in time order. We look for the trend (up, down or steady) and for ups and downs that repeat.
A moving average smooths the ups and downs. For the 3-point moving average, take the mean of three values in a row, then slide along by one.