The correct answer is: A. variable equation
A variable equation is a mathematical equation that contains one or more variables. Variables are letters or symbols that represent unknown quantities. In quantitative analysis, variable equations are used to model relationships between different variables. For example, a variable equation might be used to model the relationship between the price of a product and the quantity of the product that is sold.
The high-low method and the low-high method are both methods of linear regression. Linear regression is a statistical method that is used to fit a straight line to a set of data points. The high-low method and the low-high method are both used to estimate the slope of the line of best fit. The slope of the line of best fit is a measure of the strength of the relationship between the two variables.
A constant equation is an equation that does not contain any variables. Constant equations are used to model relationships between two or more constants. For example, a constant equation might be used to model the relationship between the number of hours that a student studies and the student’s grade on a test.
In conclusion, the most frequently used methods of quantitative analysis include variable equations. Variable equations are used to model relationships between different variables. The high-low method and the low-high method are both methods of linear regression, which is a statistical method that is used to fit a straight line to a set of data points. A constant equation is an equation that does not contain any variables.