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A chart is a graphical representation of statistical information, often in the form of a graph or diagram. Charts are used to visually represent numerical or categorical data, making it easier to understand patterns, trends, and relationships within the data. For instance, line graphs are often used to show trends over time, such as the rate of deforestation.
A line graph is used to show how a set of data changes with respect to another quantity, often a period of time. To make a line graph, a scale and intervals for the coordinate axes are chosen. The data points are then graphed and a line connecting the points drawn. Consider a table of values that represents the growth of a plant over several weeks.
Plant Growth | |||||
---|---|---|---|---|---|
Week | 1 | 2 | 3 | 4 | 5 |
Height (in.) | 1.5 | 2.3 | 4 | 6.2 | 8 |
The height data includes values from 1.5 to 8, so a scale from 0 to 10 inches with an interval of 1 inch is reasonable. The horizontal axis can represent time in weeks and the vertical axis can represent the plant height in inches. Now the points can be plotted on a coordinate plane and connected with a line.
A box plot, or box and whisker plot, can be used to illustrate the distribution of a data set. A box plot has three parts.
If a data set has outliers, they are marked as separate points to the left and/or right of the whiskers. A box plot is a scaled figure and is usually presented above a number line. The set of numbers used to draw the box plot is called the five-number summary of the data set. Each of the five numbers is labeled below.
A histogram is a graphical illustration of a frequency distribution of a data set that contains numerical data. Histograms have several defining characteristics.
A bar graph is a graphical representation of a categorical data. It is made of rectangular bars and each bar represents a category and its corresponding value. Bar graphs are commonly used to show frequency distributions, in which case they are often created using the data in a frequency table.
A pie chart is a circular chart used to represent the relative frequencies of a data set. It is also called a circle chart. These charts are divided into several slices — each representing a group of the whole data set. The following characteristics are typical of pie charts.
A pie chart allows the visualization of each individual data group when compared to the whole. Alone, however, the chart does not give information about the frequency of each group.
Pie charts might also include the relative frequency of each group written as a percentage. It is also possible to include labels to represent each group with matching colors.
A scatter plot is a graph that shows each observation of a bivariate data set as an ordered pair in a coordinate plane. Consider the following example, where a scatter plot illustrates the results gathered at a local ice cream parlor. This study records the number of ice creams sold and the corresponding air temperature.
A stem-and-leaf plot is a table that orders numerical data, which can be either discrete or continuous, and shows how they are distributed. A stem-and-leaf plot is constructed by breaking each number from the data into a stem
and a leaf.
The stem of the number is all but the last digit and the leaf is always the last digit. Stem-and-leaf plots include a key that defines how the numbers in the set are to be interpreted.