Prediction Time – What Will It Take To Make The DI Championships?

Jacob Skipper is the swimming SID at William & Mary.  He stays away from the water.

Now that conference season is upon us, one of the questions that preys upon everyone’s mind is what will it take to get in?  Below are my semi-educated guesses, along with the rationale I used to arrive at them.  This is a tool I’ve come up for my own use the last couple years, so that I can try and have a heads-up when an athlete is nearing NCAA qualification.

The Method

I took the last several years of final-invited times off the NCAA psych sheets, dating back to 2011, and calculate the year-by-year change.  Then, I use a simple formula to average all of those changes, with an extra weight to both the most recent year-change, and the year-change to the equivalent earlier year, and add that to last year’s invited time. So, for 2017, I weight the change between 2015 and 2016, as well as the change between 2012 and 2013 (the most recent year after an Olympics year).  The excel formula is average((2*mostrecent),(2*mostsimilar), N1, N2, N3, etc…), where the Ns are the other years changes (in this case, 11 to 12, 13 to 14, and 14 to 15).  The double-weight to the most recent year is a change for this season.  Also new to this year is a weight to try and correct for the error I found from last year’s predictions.  In the example:  I had projected last year’s men’s 500 free to need 4:17.01 to qualify, and the last invited was 4:17.73.  Dividing the actual by the projected gives an error of 1.002817055.  This year, once I had done the original calculation, I then multiplied it by the error factor to achieve the refined projection.

Assumptions

– Only looking at the individual swimming events.  The relays are now entirely dependent on the individual qualifications, so it’s not useful to figure out the time you need to go – it’s conceivable that a school could set the world record in (say) the 200 medley relay, but not swim at NCAAs because no one qualified individually.

– Similarly, didn’t look at the diving events.  Once you meet the regional standard, it’s entirely dependent on the competition at the zone meets.

– I only looked at the official psych sheets cut line for each year.  If there was a late-add alternate, they don’t figure in.

Disclaimer

I am in no way affiliated with the selection committee, nor am I psychic (that I’m aware of).  These are predictions and guesses, informed only by my knowledge of numbers and 10-year experience as a collegiate SID.  If you rely on these numbers, and you or your swimmer misses out on the NCAA Championships because you thought you/they were safely in and the cutoff came in lower, that’s your own mistake.

The Numbers

With no further ado, here is the table of projections.

Here is a simplified source table – the columns are what I projected for last year, what it actually took, what the absolute (in seconds) and percentage error (absolute error divided by the actual invite).  Negative numbers in the error denote that I projected a slower time than it actually took to make the meet.