The values of 'a' and 'b' if the equation of straight line trend by least square method is given by $y = a + bx$ such that $Σx=0,Σy=84,Σxy=108,Σx^2=70$ for 6 observation as are:

$a= 14; b = 1.54$

The correct answer is Option (2) → $a= 14; b = 1.54$

$y=a+bx$

$\sum y = na + b\sum x$

$84 = 6a + b(0)$

$84 = 6a$

$a = 14$

$\sum xy = a\sum x + b\sum x^2$

$108 = 14(0) + b(70)$

$108 = 70b$

$b = \frac{108}{70} = \frac{54}{35}$

The values are $a=14,\; b=\frac{54}{35}$.