השוואת שיטות

	שיטת הריבועים הפחותים המוכללת (GLS)	OLS חסין (OLS עם שגיאות תקן חסינות)
תחום	סטטיסטיקה	אקונומטריקה
משפחה	Regression model	Regression model
שנת המקור	1935	1980
הוגה השיטה	Alexander Craig Aitken	Halbert White
סוג	Linear estimator	Linear regression with robust inference
מקור מכונן	Aitken, A. C. (1935). IV.—On least squares and linear combination of observations. Proceedings of the Royal Society of Edinburgh, 55, 42–48.	White, H. (1980). A heteroskedasticity-consistent covariance matrix estimator and a direct test for heteroskedasticity. Econometrica, 48(4), 817–838.
כינויים	GLS, Aitken estimator, EGLS, feasible GLS	HC robust regression, White robust OLS, sandwich estimator OLS, OLS with robust standard errors
קשורות	3	6
תקציר	Generalized Least Squares (GLS) is a linear regression estimator that extends ordinary least squares to handle situations where the error terms are correlated or have non-constant variance (heteroscedasticity). Introduced by Alexander Craig Aitken in 1935, GLS achieves the Best Linear Unbiased Estimator (BLUE) under a general error covariance structure by weighting observations according to their precision, providing a theoretical bridge between OLS and modern linear mixed models.	Robust OLS applies ordinary least squares to estimate coefficients and then replaces the classical standard errors with heteroscedasticity-consistent (HC) standard errors — commonly called White standard errors. This leaves the point estimates unchanged while yielding valid t-statistics and confidence intervals even when the error variance is not constant across observations.