Question

The secular trend is measured by the method of semi-averages when:

• A. Time series based on yearly values
• B. Time series consists of even number of values
• C. Trend is linear
• D. None of them

Answer 1

The correct option is C Trend is linear

$\Rightarrow$ The secular trend is measured by the method of semi-averages when : $Trendislinear.$

$\Rightarrow$ Under this method the whole time series data is classified into two equal parts and the averages for each half are calculated. If the data is for even number of years, it is easily divided into two.

$\Rightarrow$ If the data is for odd number of years, then the middle year of the time series is left and the two halves are constituted with the period on each side of the middle year.

$\Rightarrow$ The arithmetic mean for a half is taken to be representative of the value corresponding to the midpoint of the time interval of that half. Thus we get two points.

$\Rightarrow$ These two points are plotted on a graph and then are joined by straight line which is our required trend line.