Which of the following statements are correct?

(A) The method of least squares determines the position of the trend line of the given time series.
(B) The trend line is called the line of best fit.
(C) The line of best fit is a line in which the sum of deviations of the actual values of the variable from their corresponding trend value is always positive.
(D) The normal equations of the trend line $y = a + bx$ are $∑y= na + b∑x$ and $∑xy = a∑x + b∑x^2$, where $n$ is the numbers of observations.

Choose the correct answer from the options given below:

(A), (B) and (D) only

The correct answer is Option (2) → (A), (B) and (D) only

Check each statement.

(A) The method of least squares is used to determine the position of the trend line of a time series → correct.

(B) The trend line is also called the line of best fit → correct.

(C) In least squares, the sum of deviations from the trend line is zero, not always positive → incorrect.

(D) For $y=a+bx$, normal equations are $\sum y = na + b\sum x$ and $\sum xy = a\sum x + b\sum x^{2}$ → correct.

final answer: $\text{(A), (B) and (D)}$