Dot plots
A list of measurements is hard to read. What picture shows every value at once, already sorted and counted?
Where you are 3 inside
What this area is about
A dot plot, also called a line plot, is a number line with one dot (or X) above it for each data value, placed over that value. Equal values stack, so the height of a stack is how often that value came up. It suits numerical data with a modest number of values, few enough that every one can be drawn, and it shows clusters, gaps, peaks and how far apart the smallest and largest values are.
How these fit together
Reading. Reading dot plots counts the stack over each value and reads clusters, gaps and peaks off a finished plot.
Making. Making a dot plot runs the same idea the other way: mark a number line in equal steps from the smallest value to the largest, then place one mark per value.
An extension. Line plots with fractions are the same display on a number line marked in halves, quarters or eighths, for lengths measured to the nearest \displaystyle \frac{1}{2}, \displaystyle \frac{1}{4} or \displaystyle \frac{1}{8} inch.
A path through it
Read a finished plot first, then make one from a list, then move to fractional number lines once fractions on a number line are familiar.
Finish here and you can group values into bins for histograms, find the median of a list with an even count, and compare two groups with back-to-back stem-and-leaf plots.