New Posts New Posts RSS Feed: Quick PY Question
  FAQ FAQ  Forum Search   Register Register  Login Login

Quick PY Question

 Post Reply Post Reply Page  <1 1112131415 16>
Author
iGRF View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 07 Mar 11
Location: Hythe
Online Status: Offline
Posts: 6499
Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Topic: Quick PY Question
    Posted: 11 Jan 13 at 5:13pm

Oh no I only opened it to get one out and now the bloody things fallen over...
Back to Top
Rupert View Drop Down
Really should get out more
Really should get out more


Joined: 11 Aug 04
Location: Whitefriars sc
Online Status: Offline
Posts: 8956
Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 5:40pm
So, how many boats of one class do people feel they need racing at a club before they are willing to make handicap adjustments, and how many races must each of those boats have done to count?
Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686
Back to Top
pondmonkey View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 12 Aug 11
Online Status: Offline
Posts: 2202
Post Options Post Options   Quote pondmonkey Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 6:22pm
3 or 4 individuals surely? Otherwise it's nothing short of a personal handicap?
Back to Top
getafix View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 28 Mar 06
Location: United Kingdom
Online Status: Offline
Posts: 2143
Post Options Post Options   Quote getafix Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 6:30pm
Originally posted by Rupert

So, how many boats of one class do people feel they need racing at a club before they are willing to make handicap adjustments, and how many races must each of those boats have done to count?
 
one short guy, in one boat, probably an obscure one, after dallying with classes sailed by more than a few 'enthusiasts' and getting nowhere, who comes last a fair bit and has a leaning towards posting contentious stuff around here?
Back to Top
RS400atC View Drop Down
Really should get out more
Really should get out more


Joined: 04 Dec 08
Online Status: Offline
Posts: 3011
Post Options Post Options   Quote RS400atC Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 7:11pm
Originally posted by pondmonkey

3 or 4 individuals surely? Otherwise it's nothing short of a personal handicap?


It would have to be more than 4.
And it would have to be random, uncorrelated individuals for such a small sample to reflect any sort of potential of the boat.
The trouble is, people do not buy boats at random, the people who are more serious about racing are very likely to buy into a class or fleet. And they will buy what their friends have, so you get a group of like-minded people racing the same class.

But it is always easy for some spreadsheet operator with no clue about statistics to believe they can put everything right, justifying gross changes with a belief that their local water is strangely different from any other in the UK.

When you sail at a small club, with only 4 or less of most classes sailing, people need to accept the numbers and get on with the racing. Once the numbers are up for debate, it gets personal, and a significant fraction will be upset.

Each year we get changes in the numbers, largely I suspect caused by flawed analysis and data skew.
The RS400 vs Laser 4000 has changed in the same direction the last few years. My boat hasn't changed, the 4000 has not changed, so either some of the numbers are wrong or the uncertainty is far greater than the changes.

 Of course the RS facelift does not exactly add clarity to the situation, but my boat is unchanged. SMODs may have step changes in their rules, more open classes will develop continuously to a greater or lesser extent. Obsolescent classes get slower on average as the sails etc age.
Back to Top
SoggyBadger View Drop Down
Really should get out more
Really should get out more


Joined: 26 Oct 10
Location: The Wild Wood
Online Status: Offline
Posts: 552
Post Options Post Options   Quote SoggyBadger Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 7:13pm
It all depends on what degree of accuracy is acceptable to you. It's been decades since I've done any stats in anger (as a Science undergraduate in the 70s) so I'm a bit rusty on the minutae but I'm extremely sceptical about the validity of these 4-dgit numbers even given the sample size the RYA have to work with. 
Best wishes from deep in the woods

SB

Back to Top
JimC View Drop Down
Really should get out more
Really should get out more
Avatar

Joined: 17 May 04
Location: United Kingdom
Online Status: Offline
Posts: 6662
Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 8:46pm
Originally posted by SoggyBadger

I'm extremely sceptical about the validity of these 4-dgit numbers even given the sample size the RYA have to work with. 

I think the source of the problem was that back in 1980 or whenever it was this was going to be the second renumbering in not too many years because they'd got too little granularity at the low wne of the scale. So by multiplying the numbers by 9.something they made d**** sure that wasn't going to happen again. But I quite agree that one point adjustments are pretty much meaningless. Normally we run a minimum of 5 point adjustments at my club.
Back to Top
Guests View Drop Down
Guest Group
Guest Group
Post Options Post Options   Quote Guests Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 8:56pm
[url]http://www.sciencebuddies.org/science-fair-projects/project_ideas/Soc_participants.shtml[\url]
You have every right to be sceptical. To have a 95% chance of being within 1% of the true PY, you need a sample size of 10,000. To get to single digit accuracy on a 4 digit PY scheme you need 1 million samples.

Back to Top
SoggyBadger View Drop Down
Really should get out more
Really should get out more


Joined: 26 Oct 10
Location: The Wild Wood
Online Status: Offline
Posts: 552
Post Options Post Options   Quote SoggyBadger Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 9:28pm
Originally posted by Peaky

http://www.sciencebuddies.org/science-fair-projects/project_ideas/Soc_participants.shtml
You have every right to be sceptical. To have a 95% chance of being within 1% of the true PY, you need a sample size of 10,000. To get to single digit accuracy on a 4 digit PY scheme you need 1 million samples.



Great find Peaky. So it seems that at club level even if you could get 10 boats (and that would have to be 10 boats of each class entered in the race) then you'd still have a margin of error of just over 30%.
Best wishes from deep in the woods

SB

Back to Top
marke View Drop Down
Far too distracted from work
Far too distracted from work


Joined: 16 Jun 08
Location: United Kingdom
Online Status: Offline
Posts: 211
Post Options Post Options   Quote marke Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jan 13 at 10:00pm
So if understand this correctly you are proposing to base your local PY adjustments on a single race with 10 competitors.

At our club, which due to tidal restrictions, doesn't run that many races each year still manages to generate ~3500 PY samples per year. 

[Nationally there are several hundred sailing clubs - if we could persuade 200 of them to press a button on sailwave or submit their spreadsheets - we might be collecting ~500,000 samples a year.  Pretty soon we are talking a real data set].
Back to Top
 Post Reply Post Reply Page  <1 1112131415 16>

Forum Jump Forum Permissions View Drop Down

Bulletin Board Software by Web Wiz Forums® version 9.665y
Copyright ©2001-2010 Web Wiz
Change your personal settings, or read our privacy policy