问题如下：
Many statistical problems arise when estimating relationships using regression analysis. Some of these problems are due to the assumptions behind the regression model. Which one of the following is NOT one of these problems?
选项：
A.Stratification
B.Multicollinearity
C.Heteroscedasticity
D.Autocorrelation
解释：
A is correct.
考点Violations of Regression Assumption
解析Stratification is not related to regression analysis. Choices B, C, and D describe situations that can produce inaccurate descriptions of the relationship between the independent and dependent variables. Multicollinearity occurs when the independent variables are themselves correlated, Heteroscedasticity occurs when the variances are different across observations, and autocorrelation occurs when successive observations are influenced by the proceeding observations.
Stratification 这是什么？
