Estimating 2019 NCAA D1 National Championship Qualifying Times

With NCAA conference championship season approaching, many swimmer’s focus is on swimming a time fast enough to get them invited to the national championship meet. Making their lives complicated is the fact that no one knows what time will be required to qualify for the meet. If you want the full details on the NCAA qualifying system (or a reminder), you can check out our detailed explanation.

There is good news for aspiring nationals swimmers. While the cut lines aren’t set in stone, they are more consistent from one year to the next than you might expect from the NCAA’s arcane qualifying system. Here is where the cut line has fallen each of the past 6 years:

Men

Women

The goal of this inspection is to try and figure out where those times will fall this year. The times generally get faster from one year to the next (about .2% per event, standard deviation .2%). Generally the majority of qualifying times get faster each year. The main exception was the men in 2016 when 8 of 13 times were slower than the year before. Before we blame that on an Olympic year, it’s worth noting that the women’s qualifying times were slower in only 2 of 13 events that year. More likely, this minor slow down can be explained by simple random noise in the data.

The women’s times last year took a bit larger of a jump forward than normal. This was because the cut line fell at 37 instead of around 40 like it normally does. That jump of a couple places was worth a tenth or two in most events.

The consistency of the year-to-year change in the data is enough to provide a decent estimate of what the qualifying times will be this year. However, we can do better because we know more information than just last year’s qualifying times. We also know how swimmers have been performing so far this year. A comparison of the current year’s results as of today to the previous year’s results as of January 31st has some correlation with how qualifying times change one year to the next.

To model qualifying time change, I only looked at swimmers currently ranked 25th-70th. For the most part, this represents the swimmers on the bubble to make the meet.  A typical men’s cut line is around 30 and the women’s cut line typically is around 40. I tried different ranges for the men and women because of the different cap numbers, but this range seemed to work best for both. I also tried adding in variables for stroke and distance but they did not improve the estimate at all. This historic in season time change data explains 41% of the variability in the end of year time change data for the men and 22% for women. The trend lines are below. Negative is faster, positive is slower. The red lines represent a 95% confidence interval of estimation.

Men

Women

With that model in place, we can now use it to guess the cut times this year. The best guess of the model is reported as the ‘Estimated Cut’ below. However, it’s unlikely that the cut will fall exactly on any of the estimates. Instead, it’s likely to fall within a range of times around the estimate. The model believes there is a 95% chance the real cut line will fall between the ‘Estimate Lower Bound’ and the ‘Estimate Upper Bound’ listed below.

For the most part the model is pretty conservative predicting small time changes in each event. That is no guarantee that the qualifying times will be faster or slower where the estimate is faster or slower. Even if every assumption of this model is correct, I would expect at least 1 time to fall outside the predicted ranges. That being said, I also expect the majority of the times will fall within the estimate ranges and will fall closer to the center of the estimate range than the outer bounds.

Men

Women

The “on the bubble” swimmers are faster this year for the men in 9 of 13 events. The biggest jump came in the 200 free, hence the relatively large .38 predicted improvement in qualifying time. the biggest drop off came in the 1650, the only event where the model thinks the qualifying time will be slower.

The women’s bubble swimmers are faster in only 4 of 13 events this year. The main events that improved are the breaststrokes. The model predicts that the 100 qualifying time will dip under 1:00 for the first time ever and under 2:10 in the 200. Most of the other cuts are predicted to stay about the same.

I will not use this model to guess the cuts in the lower divisions. The cut line in D3 is too unstable year to year for this type of model to be useful estimating the qualifying times there and they keep changing the rules. The current rules make guessing the D3 lines more an exercise in guessing where the cut line will fall than guessing the strength of the overall field. D2 has hard cuts so there’s nothing to estimate.