Retest Delta
A retest delta is the change from your pre-drill baseline to your post-drill retest, on the metric your fix targeted. It shows if one session moved the needle.
While an improvement delta tracks long-term progress, the retest delta is the immediate feedback loop for a single session. After a focused drill block, you record the same type of swing under the same conditions. Then you compare the key metric to what you recorded before drilling. A significant positive retest delta is evidence that the session produced real change. A negligible one is an honest signal that either the drill wasn't effective or the pattern hasn't transferred yet.
Do your retest immediately after the drill block while the motor pattern is fresh — waiting until the next day introduces confounding variables and makes the delta harder to attribute to the specific drill.
Record the exact number of drill reps completed and any cues used alongside your retest data. As a result, future sessions can replicate the dose and cue combination that produced a confirmed positive delta.
Example
Pre-drill average club path: +7 degrees; post-drill retest average: +3 degrees. Retest delta of -4 degrees is a meaningful session win.
How it shows up on video
Compare the skeleton overlay at impact between your pre-drill and post-drill clips for the specific phase the drill targeted. A visible positional change at the target position should correlate with a positive retest delta in the corresponding metric — if you see no visual change, expect a small or zero delta.
Common mistakes
- Waiting until the next day to run the retest. The post-drill retest is most informative immediately after the drill block while the motor pattern is fresh. Waiting introduces confounding variables.
- Changing conditions between the pre-drill and post-drill sets (different club, different target, different warmup) — uncontrolled variables make the retest delta uninterpretable.
- Recording the retest without matching the same number of swings as the pre-drill set — unequal sample sizes make delta interpretation unreliable, especially at small sample counts.
- Treating a positive retest delta as a permanent fix. The post-drill delta confirms the pattern changed in the session. A follow-up retest in the next session confirms whether it was retained.
In SwingVantage Motion Lab
Motion Lab's before-after comparison mode is specifically designed for retest deltas — load the pre-drill clip as the reference and the post-drill retest as the current. The overlay immediately shows whether the target position shifted, providing a visual sanity check alongside the numerical delta.
Related terms
- Baseline MeasurementA baseline measurement is the first recorded data point for a metric, captured before training begins, that all future improvement is measured against.
- Improvement DeltaAn improvement delta is the measured change in a metric from your baseline to your most recent measurement. It is the hard number behind "did I get better?"
- RetestA retest is a short follow-up protocol attached to each recommendation. It sets the shot count, metrics, and success criteria that show whether a fix worked.
- Signal vs NoiseSignal is the real, repeatable pattern in your swing data; noise is the random variation that looks like a pattern but isn't. Distinguishing the two is what separates useful analysis from false precision.
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