This method allows for time calculations for (X) and (Y) values, and is based on the method of least squares. Basically, this method is to find the line where the sum of the squares of the deviation of each point of data from the line is a minimum. The sequence of variables should mirror job sequence in the field. Upon chart completion, it is a good idea to test the chart by sending it to your customer plants. The objective is to check the chart for ease of use accuracy, and any mistakes that may have occurred during its development. If plant verification responses reflect non-acceptance, then corrective action may include a simple modification to the chart, or additional restudy of the operation to generate new raw data.