When it comes to diagnostic plots in R, the use of standardized or studentized residuals is a common point of confusion for many analysts and researchers. In this article, I will explore the differences between standardized and studentized residuals, and discuss how they are used in diagnostic plots in R.

## Standardized Residuals

Standardized residuals, also known as internally studentized residuals, are obtained by dividing the residual by its standard error. This allows for a comparison of residuals across different observations, making it easier to identify outliers and influential points in a dataset. In R, standardized residuals can be obtained using the `studres()`

function from the `lattice`

package.

## Studentized Residuals

Studentized residuals, on the other hand, are obtained by dividing the residual by an estimate of its standard deviation. Studentized residuals are particularly useful for identifying influential points and outliers. In R, studentized residuals can be obtained using the `studres()`

function from the `stats`

package.

Now, you might be wondering which type of residual is used in the diagnostic plots in R. Well, the answer is that it depends on the specific diagnostic plot being used. For example, in the `plot.lm()`

function for linear regression models, R uses studentized residuals by default. On the other hand, in the `qqPlot()`

function from the `car`

package, standardized residuals are used.

## Personal Perspective

As someone who has spent a considerable amount of time working with regression models and diagnostic plots in R, I have found that understanding the distinction between standardized and studentized residuals is crucial for effectively identifying influential points and assessing model fit. In my experience, being able to interpret these diagnostic plots with confidence has significantly improved the quality of my analyses and the reliability of my results.

## Conclusion

In conclusion, the use of standardized and studentized residuals in diagnostic plots in R plays a critical role in assessing the assumptions and performance of statistical models. By gaining a deeper understanding of these concepts and their implementation in R, analysts and researchers can make more informed decisions and produce more robust analyses.