Such patterns sometimes can be used to make predictions about the phenomena being graphed. It takes two numbers to locate a point on a map or any other flat surface. The numbers may be two perpendicular distances from a point, or an angle and a distance from a point. The scale chosen for a graph or drawing makes a big difference in how useful it is. Estimates can be based on data from similar conditions in the past or on the assumption that all the possibilities are known.
Probabilities are ratios and can be expressed as fractions, percentages, or odds.
The mean, median, and mode tell different things about the middle of a data set. Comparison of data from two groups should involve comparing both their middles and the spreads around them. The larger a well-chosen sample is, the more accurately it is likely to represent the whole. But there are many ways of choosing a sample that can make it unrepresentative of the whole. Events can be described in terms of being more or less likely, impossible, or certain.