Sunday, June 22, 2008

Should mileage units be gallons per 1000 miles?

Mileage is generally reported in miles per gallon (or kilometers per litre for the rest of the world). This seems to make sense. The consumer will want to know how far they will be able to get with the gasoline (petrol or paraffin for you non-Americans) they buy. Well, not exactly.

That might be a good metric if you have a fixed fuel budget and your travel plans followed from this. But most people buying automobiles aren't in that position. Most car shoppers have a certain amount of driving they need to do and are looking to keep their expenditures down. It should therefore make more sense to report mileage as the reciprocal (like gallons per 1000 miles for example).

While the two are mathematically equivalent, reciprocals scale differently. Most people will make bad decisions with the opposite ratio. Check out the video below for an explanation.

There are many examples of things like this all over. Let's take sunscreens for example. The SPF rating represents the equivalent protected exposure to UV rays in minutes to 1 minute exposure without the sunscreen. For example, 15 minutes of exposure to the sun while wearing SPF15 sunscreen gives you the same UV exposure as 1 minute unprotected.

But how much UV radiation is actually blocked? That can be calculated using the formula (1 - 1/SPF) * 100%
SPF5 blocks 80% of UV radiation.
SPF15 blocks 93% of UV radiation.
SPF45 blocks 98% of UV radiation.
SPF100 blocks 99% of UV radiation.

While something with a very high SPF rating may seem very impressive, I think anything higher than SPF15 is a waste.

And of course the way mileage is reported should be changed.

Thursday, June 05, 2008

2008 Anti-Superstition Party this Friday 13th!

Next Friday, June 13th is the Freethought Society of Philadelphia's 2008 Anti-Superstition party. For those who've been reading this blog for a while (back when I actually used to write more) may remember my visit to the 2006 Anti-Superstion party. It is likely that I will be the Lucky Leprechaun once again. ;-)

This year's party looks to be a lot of fun. It will be held at the Radisson-Warwick Plaza Hotel and the guest of honor will be none other than "The Amazing" James Randi. So if you can't make it out to Las Vegas for TAM6 and you'll be near Phily on the 13th, you might want to consider stopping by.

You'll also get to meet Dr. Stephen Uhl, former priest-turned-psychologist. How can you miss that???