Scottish Referendum – Eve of Count Forecast

This forecast takes account of the final MORI poll for the Evening Standard.

This is an Election Day prediction. This means it is a forecast on the day of the Election as to what the actual Yes vote will be.

The Election Day “centre point” of the prediction is 47.90%. This is the middle point of the distribution of likely outcomes based upon recent polling and other market data.

The Election Day “Probability of Yes being greater than 50%” prediction is 4.01%.  This means that when we run 10,000 simulations of the referendum based on current polling trends and the variances within them, Yes would win only 401 times.

The table below shows the 50% and 95% confidence intervals for the Yes vote.

Date Yes% 50% Intervals 95% Intervals
11th September 48.18 47.14 – 49.23 45.15 – 51.21
12th September 47.82 46.76 – 48.88 44.74 – 50.91
13th September 47.40 46.16 – 48.64 43.80 – 51.00
14th September 48.95 47.60 – 50.31 45.02 – 52.89
15th September 48.36 47.26 – 49.46 45.15 – 51.57
16th September 48.50 47.08 – 49.93 44.36 – 52.65
17th September 47.60 46.96 – 48.14 45.84 – 49.26
18th September am 47.78 47.28 – 48.28 46.32 – 49.24
18th September pm 47.90 47.45 – 48.36 46.58 – 49.22

Is this your final prediction? 

Yes. We now have all the data tables from all the polls. There is nothing left to do now but find out the result.

What is the main feature of the last few days of polling?

Undoubtedly the main observation has been the narrowing of the confidence intervals of our prediction. With so many polling firms delivering results in the same area, it is clear that the margin of error has contracted significantly and this has contributed to the reduction in the probability of a Yes victory. If you compare our prediction this morning to those on the 13th, today we have a higher centre point but much shorter confidence intervals.

What if your prediction is wrong?

If our prediction is wrong then all the polling firms are wrong. Given that there has never been a referendum in Scotland on this issue before, weightings and accounting for those who previously haven’t voted may be compromised. However, in the absence of any empirical evidence that the polls are biased, we must treat them as unbiased barometers of public opinion.

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