A scatter plot, also known as scatter chart, scatter diagram, or scattergraph, is a type of mathematical chart which displays a set of data, as a collection of individual points, using two variables on the two Cartesian coordinates. Each point represents one data, showing the value of both the variables for that particular data. Scatter plot is one of the seven basic tools used in quality control. It is also used in finding out the future trends by studying past data.
The use of scatter plots is when there is a huge data set and the requirement is to obtain the relationship between two variables, if any exists. Unlike line graphs, here we get a scattered set of points which are used to get ‘best fit line’ or ‘trendline’. Closer the points to this line, stronger the correlation between the two variables.
Three scenarios emerge:
Positive correlation – the slope of the line is from left to right (rising); as the value of one variable increases, the value of other also increases
Negative correlation – the slope of the line is from right to left (falling); as the value of one variable increases, the value of other decreases
No correlation – All points are scattered and no best fit line could be drawn
Correlation between height and weight of an individual can be found out using this data set:
The corresponding scatter plot gives a positive correlation.