Choose the following data:
|
Year |
2008 |
2009 |
2010 |
2011 |
2012 |
|
Production (in tons) |
9 |
17 |
23 |
29 |
40 |
A straight line trend by the method of least squares is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $y=23.6+7.4 x$
$\text{Take } x = -2,-1,0,1,2 \text{ for years } 2008,2009,2010,2011,2012$
$y = 9,17,23,29,40$
$\sum y = 118,\;\; \sum x = 0,\;\; \sum x^2 = 10$
$\sum xy = (-2)(9)+(-1)(17)+0(23)+1(29)+2(40)$
$\sum xy = -18 -17 + 29 + 80 = 74$
$b = \frac{\sum xy}{\sum x^2} = \frac{74}{10} = 7.4$
$a = \frac{\sum y}{n} = \frac{118}{5} = 23.6$
$y = a + bx$
$y = 23.6 + 7.4x$
$x = \text{Year} - 2010$
$y = 23.6 + 7.4(\text{Year} - 2010)$
The straight line trend is $y = 23.6 + 7.4(\text{Year} - 2010)$.