Final answer:
In FQY analysis, the residual standard deviation is not used. Instead, a graphical approach is used to identify outliers by drawing extra lines on a scatter plot. The residual standard deviation measures the variation of points not close to the regression line.
Step-by-step explanation:
In FQY analysis, residual standard deviation is not used. Instead, a graphical approach is used to identify potential outliers by drawing an extra pair of lines that are two standard deviations above and below the best-fit line on a scatter plot. Any data points outside these lines are flagged as potential outliers. This approach is easier and can be done using TI-83, 83+, or 84+ calculators. By comparing the residuals calculated from the scatter plot with twice the standard deviation, we can determine if there are outliers. If an outlier is identified, it can be removed from the data and a new line can be fitted to the remaining data. This can help improve the overall fit of the data. The residual standard deviation is not used in FQY analysis because it measures the variation of the points that are not as close to the regression line. FQY analysis focuses on identifying outliers and improving the fit of the best-fit regression line to the data.