Let x and y be the year and values The Straight line equation is
y = a + bx
Normal equations are –
na + bΣx = Σy ………… (1)
aΣx + bΣx2 = Σxy ………….(2)
Here x̄ = 1992
From (1) 7a + b.O = 3106
∴ a = 443.71
From (2) a.O + b.28 = 2045
∴ b= 73.04
∴ The fitted straight line trend equation is
ŷ = 443.71 + 73.04x
Trend value (ŷ) for 1989; Here x = -3
∴ ŷ1989 = 443.71 + 73.04 (-3) = 443.71 – 219.12
ŷ89 = 224.50
Trend value for 1990 ; Here x = -2
ŷ90 = 443.71 + 73.04(-2) = 297.63
Similarly all remaining trend values can be obtained by substituting
x = -1,0,1,2 and 3 Straight line trend:
