• Blog home
  • Elections
  • Polling
  • Sport
  • Weather
  • Forecasting
  • Diversity
  • Stats Training
  • Misc
  • Archive
  • Twitter
  • Back to Marriott Statistical Consulting

Nigel Marriott's Blog

An independent statistician using data to understand our world and to predict the future

You are here: Home / Archive / UK Weather Tracker #6 – July 2017

UK Weather Tracker #6 – July 2017

August 3, 2017 By Nigel

My latest UK weather tracker shows that July has been an unremarkable month and it would appear that the summer in 2017 will also be unremarkable.  Believe it or not, I have predicting this for the last few years and I will explain why in a separate post in September.

As always, the meteorological year starts in December which is why July appears as the 8th data point in the charts below.  More information on the layout of the charts can be found in this post.

July is the first month this year where all 6 variables shown in the chart were between the historical upper & lower deciles so it should be no surprise to hear me describe July as an unremarkable month.  In fact, “unremarkable” months are actually more remarkable than you might think.  Consider the definition of a decile.  The probability of a month being lower than the lower decile is 10% by definition and conversely the probability of being above the upper decile is also 10%.  This means there is an 80% chance of any month being between the upper and lower deciles.  If each variable has a 4 in 5 chance of being between the deciles, what is the probability of all 6 being between the deciles?

Before calculating this, we need to assume that the 6  variables have no relationship with each other which is a dangerous assumption to make and one that I will be exploring in September but for now, I will make this so.  Then the probability of two variable being between the deciles will 4/5 x 4/5 or 0.8^2.  With 6 variables, the equivalent calculation is 0.8^6 which is equal to 0.262 or 26.2%.  So an “unremarkable” month would be expected to occur once in every 4 months which is actually not that common and therefore should be regarded as remarkable rather than unremarkable!

The converse of this is that for 3 in 4 months, we can expect at least of the variables to have an “uncommon” value perhaps even a near record value.  This is a good demonstration of the dangers of analysing MULTIVARIATE data sets.  If you are tracking many indicators at the same time, the odds of all indicators being unremarkable are in fact quite low.  Yet the human tendency is to observe unusual values and to ask why is that happening?  In fact, nothing is happening except normal chance.  This is a variant of the false positive fallacy that humans are prone to.

Economic indicators are especially prone to this illusion since there are so many indicators available and if you are determined to present a positive or negative picture of the current economic climate, then you can nearly always find an indicator or indicators that will prove your point.  Such claims are quite common these days with the debate about the effects of Brexit and I intend to start an economic indicator tracker in the near future to help people to make sense of the latest economic statistics.

Filed Under: Archive Tagged With: Presenting data, Weather, Weather Tracker

Search this site

More blogs

UK Weather Trends #27 – Summer 2023

The hottest June on record resulted in the 8th warmest summer on record in the UK.  However, rain … [Read More...] about UK Weather Trends #27 – Summer 2023

UK Weather Tracker #79 – August 2023

A warmer than normal but otherwise unremarkable weather in August brings the 2023 UK meteorological … [Read More...] about UK Weather Tracker #79 – August 2023

UK Weather Tracker #78 – July 2023

The UK weather gods followed up the hottest June on record with the 5th wettest July on record.  In … [Read More...] about UK Weather Tracker #78 – July 2023

Pay Gap Data #6 – Where can I find gender pay gap data for 2022?

This post was updated on 9th July 2023 with the latest data The government requires all … [Read More...] about Pay Gap Data #6 – Where can I find gender pay gap data for 2022?

UK Weather Tracker #77 – June 2023

June 2023 was the hottest on record in the UK.  It was also the 4th sunniest & 7th widest … [Read More...] about UK Weather Tracker #77 – June 2023

Subscribe to Our Newsletter

Join our newsletter mailing list

Receive latest news, articles and offers

Select the categories of interest:

We are GDPR compliant. Read our privacy and Cookie policy for more info.

Check your inbox or spam folder to confirm your subscription.

Copyright © 2023 ·Registered in England, Company No. 5577275, VAT No. 883304029. Registered Office – 65 Bristol Road, Keynsham, Bristol, BS31 1EG