Final answer:
The purpose of constructing a joint frequency distribution is to analyze the relationship between two variables, providing a clear visualization of how often certain combinations occur together.
Step-by-step explanation:
The reason for constructing a joint frequency distribution is D) To help analyze the relationship between two variables. By organizing the data into a table that displays how often certain combinations of the variables occur together, it allows for a clearer visualization of potential patterns or correlations between them. This can be especially useful when looking to understand how one variable might predict, affect, or relate to another. It is important to note that the joint frequency distribution itself simply displays the data and does not measure the spread or show the average between the variables, nor does it determine a trend on its own. However, it lays the foundation for further statistical analysis, such as constructing scatter plots, calculating correlation coefficients, or eventually determining regression lines, all of which delve deeper into the relationship dynamics.