Date: Thu, 20 Mar 2003 00:29:35 -0500 (EST) From: "Keith F. Lynch" <kfl at keithlynch.net> To: WSFA members <WSFAlist at keithlynch.net> Subject: [WSFA] Re: Predicting who will be at WSFA meetings Reply-To: WSFA members <WSFAlist at keithlynch.net> ronkean at juno.com wrote: > You presumably mean that 5149 is the cumulative recorded attendance > over that time period, (but just among those 143 people), much the > same way that an airline might report carrying a million passengers > in a year, even though many of those million were repeat customers > during the year. Right. That's not counting people who only showed up once or twice. > It occurs to me that an instance of non-attendance is also a data > point, so there would be 27,456 (143 x 192) data points in all, ... That's one way to look at it. But a sparse matrix is best represented only by what's present, not by what's absent. Otherwise, why not list all six billion people, most of whom have never been to WSFA, and get hundreds of billions of data points? > Doubtless you will be able to construct some formula which has > predictive value, one that has inputs such as past attendance with > time weighting, weather and traffic conditions, meeting location, > competing events, time of year, time of the month and proximity to > major holidays, etc. Yes, if I went to that much work. Which I won't. And such a model would be worthless, anyhow. A model can't contain more complexity than the data it attempts to explain, otherwise it can explain everything and nothing. In other words, I could plug in any past meeting into such a model, and it would correctly "predict" who would be there. But for future meetings it would be utterly worthless. > But each attendee is different; ... It's remotely possible that I will look at men and women separately, or Maryland and Virginia residents separately. But trying to push the data any further would be pointless. What can anyone make of your recent attendance, or rather non-attendance: 2000 |2001 |2002 |2003 J F M A M J J A S O N D|J F M A M J J A S O N D |J F M A M J J A S O N D |J F M VMMVMVBVMVMMVMVCMVMVPVM|VMVMVMVMVMvMVMMVVMVMVMVM|VMVMVMVMVMVMVMMVVMVCVMVM|VMVxV ** * ** | ** * *** ** * *| * * * * * | Will you be at the next meeting? That's up to you. -- Keith F. Lynch - kfl at keithlynch.net - http://keithlynch.net/ I always welcome replies to my e-mail, postings, and web pages, but unsolicited bulk e-mail (spam) is not acceptable. Please do not send me HTML, "rich text," or attachments, as all such email is discarded unread.