Obscure statistics

[DRT]

Maybe this explain why I still have those old green tiles in my kitchen

Derek

[Conky]

My parents both died at 53. My paternal grandfather at 51 and his father at 49.

With that genetic disposition, I wont be drinking £35,000 worth of Port, do you think you all have a responsibilty to get the good stuff out when I'm about?

Us butterflys, (thats colourful, dramatic, eye-catching, but brief), have to make the most of life.

Alan

[jdaw1]

(∑n)²/∑(n²) ≈ 10.66 as of a fraction of an hour ago.

[Alex Bridgeman]

Pardon? What does n represent to give a result of 10.66? And is that exactly 10.66 or are you pointing out that the fonts available on the board do not permit the recurring symbol to be shown?

[jdaw1]

Imagine a bulletin board with 4 members, whose number of posts are 1000, 1000, 1000 and 1. How many members does this bulletin board have? Well, really, in an activity-weighted sense, 3.

Mathematically the natural way to capture this is (∑n)²/(∑n²), that is, the square of the sum divided by the sum of the square: 1000+1000+1000+1 = 3001; 1000²+1000²+1000²+1² = 3000001; so (∑)²/(∑²) = 3001×3001÷3000001 ≈ 3.002.

And in an activity-weighted sense, has ≈10.66 (not recurring) members.

[jdaw1]

Another example: ten members have posted, 88, 53, 33, 20, 12, 7, 4, 3, 2, 1 times, so ∑n=223 and ∑n²=12265. Thus the activity-weighted number of members = (∑n)²/(∑n²) = 223×223÷12265 = 223÷55 ≈ 4.0545454. Now go back and look at the data: an answer of about 4 doesn’t look obviously wrong.