Time Series Analysis

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The sum of Seasonal Indices based on monthly data over a year should be

• Calculated from the value of the season divided by the seasonal average

• Dependent on the actual sales

• The same as the quarterly average

• 12 (or 12.001 or 11.999 depending on rounding errors)

Deseasonalised Data can be found by:

• Dividing actual sales by the seasonal index

• Dividing the seasonal index by the actual sales

• multiplying seasonal index by the actual sales

• multiplying the seasonal index by the deseasonalisted data

The actual figure can be found by...

• Dividing the deseasonalised figure by the seasonal index

• Dividing the seasonal index by the deseasonalised figure

• Multiplying the deseasonalised figure by the seasonal index

• Dividing the data value by the seasonal average

In Q1 the SI was 0.8;

in Q2 the SI was 1.2;

in Q3 the SI was 0.3;

So in Q4 the SI was...

• 0.7

• 2.3

• 2.7

• 1.7

In Q1 the SI was 0.5;

in Q2 the SI was 0.8;

in Q3 the SI was 1.3;

So in Q4 the SI was 1.4;

What can be said about the data:

• It is cyclic

• There is no trend

• There is a positive trend

• There is a negative trend