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General Mathematics · Unit 3 · Time series analysis · Analysing time series data

Deseasonalise a time series by calculating the seasonal indices using the average percentage method, including the use of spreadsheets.

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Question 1

The table shows the quarterly electricity consumption (in megawatt hours, MWh) for a regional shopping centre over two years. Deseasonalise the data and determine the deseasonalised electricity consumption for Quarter 3 of 2025.

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Question 2

A café records the average number of customers per quarter over two years. The table shows the actual customer counts and the seasonal indices calculated using the average percentage method with the mean. Determine the deseasonalised customer count for Q3 in Year 2.

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Question 3

A furniture retailer records sales revenue (in $1,000s) for each quarter over two years. The data is shown in the table below. Calculate the seasonal indices using the average percentage method and determine the deseasonalised sales revenue for 2024 Quarter 3.

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