Can anyone explain this? For the 12 years leading to my retirement I sent every employee a birthday card every year. The numbers employed waxed and waned from 76 minimum to 91 maximum. During that period not a single birthday occurred during the month of August. I have checked through ONS and statistically there is no difference in total national numbers born for each month. The company was located in Exeter (cue a gag there) and had a typical male/female mix. Any suggestions?
I’ll have a go at working out the odds, fag-packet style.
You say number of employees ranged from 76 to 91 – so let’s assume an average of 84. Lets also assume you took on a new employee every 8 months (3 every two years) for 12 years …. So in all the number of people employed at some point was 84+ 18 = 102 employees.
Now the chances anybody NOT having a birthday in August is 11 in 12 (ignoring the fact not all months have the same number of days for simplicity) = 0.916 (or 91.6%).
This means that the chance s of none of those 102 employees having an August birthday is 0.916 x 0.916 x 0.916 x….. for 102 times or mathematically = 0.916^102 = 0.0001298 (or 0.01298%).
However, there are 12 months of the year that this could have happened in so the chances of any month catching your attention like this is multiplied by 12 (you'd have said the same if it was June say) so the actual chance is 0.001298 x 12 = 0.001558 or approximately 0.16%.
So yes, it is of course very unlikely – but not ridiculous. It’s about the same chance as you being selected if they randomly chose 25 people from the crowd of 16,000 people at Home Park.
The other thing to remember is that as we go through our lives we have many opportunities (almost infinite) for weird and wonderful things to happen to us that have a tiny probability but we will only ever notice the ones that do. In other words – it would actually be bizarre if weird ‘coincidences’ didn’t happen to you at some time or another, yet when they do the temptation is to marvel about it and put some mystical significance on them (not that I'm saying you are here).