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:

0.684

Step-by-step explanation:

According to the scenario, computation of the given data are as follows

Seasonal index = Average value for July ÷ Average over all months

Where, Average value for July = ( 110 + 150 + 130 ) ÷ 3

= 390 ÷ 3 = 130

And, average over all months = 190

So by putting the value in the formula, we get

Seasonal index = 130 ÷ 190

= 0.684211 or 0.684

Hence, approximate seasonal index for July is 0.684.