Public Poll Average Calculations
This page is a permanent page which will have attached to it the excel spreadsheet which has all the calculations used for the public poll average.
The average is both size and time weighted. The calculations and assumptions are:
- Weighting is proportional to sample size. The sample size excludes undecided voters when this is known as poll results are expressed as a percentage of decided voters.
- The older a poll is, the less weighting it has. The age of the poll is calculated as the difference between today’s date and the
last day the poll was conductedmid-point of the dates the poll was conducted over. If this gap is one week or less, then the weighting is 100%. Once a poll is more than 38 days old the weighting is 0%, and between 8 and 38 days inclusive it declines proportionally every day. So a 20 day old poll is weighted 61% and a 24 day old poll is weighted 48%. This means that all polls less than a week old have equal weighting and any poll more than a monthand a week old falls off completely (as they should have been replaced by then if regular). As during the campaign period polls tend to be released weekly instead of monthly, only the latest poll for each pollster is included.
- The weighted average percentages are shown in the graphic on the main sidebar.
- The number of electorate seats a party will win is assumed to be the status quo, except when a public poll has clearly shown otherwise. This is a very conservative estimate and no projections are made on the basis of any standard swing in the overall national vote. So it is an assumption not a prediction.
- The St Lague formula is used to calculate total number of entitled seats
- A number of possible Government combinations are shown. They are automatically bolded if they form a majority able to govern.
- Due to the weighting by age of poll, the weighted average changes slightly every day, even if there is no new poll.
- One page shows the likely MPs in Parliament. It lists the Electorate MPs (based on above assumption) and the List MPs for each party. Where a party has yet to file a party list, rankings are done based on current Caucus rankings.
Feedback is welcome on the methodology and assumptions, as well as suggestions for new features or improvements. Are there other graphs or tables people would like to be able to incorporate in their own blogs?