Consider the following data :

A straight line trend by the method of least square is :

$y=23+6.9x$

The correct answer is Option (4) → $y=23+6.9x$

To find the straight-line trend,

$y=a+bx$

$∑y=9+18+21+29+36=115$

$∑x=-2+(-1)+(0)+(1)+(2)=0$

$∑xy=-18-18+0+29+76=69$

$∑x^2=(4)+(1)+(0)+(1)+(4)=10$

$a=\frac{∑y}{n}=\frac{115}{5}=23$

$b=\frac{∑xy}{∑x^2}=\frac{69}{10}=6.9$

$∴y=23+6.9x$