A seasonal index for a monthly series is about to be calculated on the basis of three years' accumulation of data. The three previous July values were 110, 150, and 130. The average over all months is 190. The approximate seasonal index for July is A) 0.487 B) 0.684 C) 1.462 D) 2.053 E) cannot be calculated with the information given

B) 0.684

Explanation:

For computing the approximate seasonal index, first we have to determine the average value for three months which is shown below:

= Previous July values : number of values

= (110 + 150 + 130) : 3

= 390 : 3

= 130

Now the approximate seasonal index would be

= Average of three months : average over all months

= 130 : 190

= 0.684