![]() If we see the correlation between the student’s height and arm length exhibit a trend, we can estimate the arm length of a student with a certain value of height given and vice-versa. The scatter graph shows information about the height and the arm length of each of 8 students in Year 11. There is no demonstrated connection between the two variables.Įdit this Diagram Scatter Chart Example: Arm Length on Grade 11 ![]() The value of Y seems to be related to the value of X, but the relationship is not easily determined. The value of Y decreases slightly as the value of X increases. The value of Y increases slightly as the value of X increases. The value of Y decreases as the value of X increases. The value of Y increases as the value of X increases. The following types of scatter diagrams show in the table tell about the degree of correlation between variable X and variable Y. The degree of correlation is denoted by “r”. The more the points plotted are closer to the line, the higher is the degree of correlation. The more the points plotted are scattered over the chart, the lesser is the degree of correlation between the variables. The degree to which the variables are related to each other depends on how the points are scattered over the chart. This shows that there is a relationship between the speed of vehicles and accidents happening on the highway. Once the diagram is completed, you notice that as the speed of vehicle increases, the number of accidents also goes up. You select the two variables: motorcycle speed and number of accidents, and draw the diagram. Thus, we can use a scatter diagram to examine theories about cause-and-effect relationships and to search for root causes of an identified problem.įor example, we can analyze the pattern of motorcycle accidents on a highway. While the diagram shows relationships, it does not by itself prove that one variable causes the other. Most often a scatter diagram is used to prove or disprove cause-and-effect relationships. The pattern of their intersecting points can graphically show relationship patterns. One variable is plotted on the horizontal axis and the other is plotted on the vertical axis. The figure below shows an example of a line of best fit where an outlier located at (3.5, 5.5) is ignored since most of the points are relatively close together except for said point.View and play PowerPoint presentations online.Ī scatter diagram (Also known as scatter plot, scatter graph, and correlation chart) is a tool for analyzing relationships between two variables for determining how closely the two variables are related. The dots above and below the line should be more or less equal in distance from the line.There should be approximately as many points below the line of best fit as there are above it. The line of best fit does not necessarily need to contain any of the points in the scatter plot.Ignore any outliers as they are not part of the linear relationship between the two variables.Given that two variables seem to have a linear correlation based on the scatter plot, the following guidelines can be used to sketch a line of best fit: The two variables below do not exhibit a discernible pattern, so they have no correlation. In this case, the line of best fit is a parabola, so the data has a non-linear correlation. Although the two variables in the figure below do not exhibit any linear correlation, we can see that they do still have a pattern. This is also shown by the fact that the line of best fit has a negative slope.Ī non-linear correlation is one in which a pattern exists between the two variables that cannot be described by a straight line. In the scatter plot below, variable 2 decreases as variable 1 increases, so the variables have a negative correlation. When two variables have a negative correlation, one variable increases as the other decreases. In the scatter plot below, the red line, referred to as the line of best fit, has a positive slope, so the two variables have a positive correlation. Positive correlationĪ positive correlation is one in which the two variables increase together. Scatter plots can show various types of correlations between variables. Below is a scatter plot showing the relationship between the cost and weight of some product: Scatter plots are often used when studying the relationship between two variables. Home / probability and statistics / descriptive statistics / scatter plot Scatter plotĪ scatter plot is a type of plot that displays values, typically for two variables, using cartesian coordinates.
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