Using Hit Rate to Gauge Success

I've mentioned before that velocity isn't the best measure of a team's progress.  Instead, we often find accuracy to be a better indicator of a team's long term success.  Since many teams still find value in having a metric with which they can plot their success, why not use one that measures how accurate they're becoming?Hit Rate is a simple metric that describes a team's accuracy over time.  In particular, it measures how close a team's forecasted velocity is coming to its actual velocity each sprint.We can calculate it using the simple formula below...

Let's Try Some Examples

Imagine that a team forecasted a velocity of 20 points for the first sprint. However, one of the stories turned out to be a bit more difficult than expected which slowed down their progress. In the end, they only completed 17 of the 20 forecasted points. Let's plug that into our Hit Rate formula to see how they did...

This tells us that the team had a Hit Rate of 85...or that they hit 85% of the velocity they originally forecasted. Note that the $latex \times 100$ at the end of the formula is only there to give us a nice percentage to work with.Let's try another one.  Imagine that the next sprint the team forecasted a velocity 18 points, but two of the stories turned out to be a simpler than expected.  This allowed them to finish early, which let them pull an additional story into the sprint.  The end result was that the team completed 2 more points than originally forecasted.  Let's plug these numbers into our formula to see how this windfall affected their Hit Rate...

This time we see the team had Hit Rate of 111%, which means that they actually completed 11% more work than originally forecast.

Hit Rate as a Trend

If either of these cases sound familiar it's because they're quite common in young scrum teams.  In fact, if you track Hit Rate from a project's outset you'll likely see a pretty erratic pattern in the beginning.  However, if you're willing to pay attention to and learn from your Hit Rate, you should start to see it settle near 100% over time.

What Your Hit Rate Can Teach You

Although some occasional wavering in your Hit Rate is to be expected, sharp trends away from 100% can reveal much about a team's tendencies.For example, is your Hit Rate consistently trending down?  If so, then the team is likely overcommitting to the amount of work they can complete each sprint.  Work with them during Sprint Planning to keep the lowest priority stories in the backlog rather than bringing them into the sprint.What if your Hit Rate is consistently trending up?  This likely means that the team can take on more work than they're selecting at the Sprint Planning meetings.  Work with them to gradually bring in a bit more work each sprint until the Hit Rate closes in on 100%.  This will build their confidence and help them see what they're really capable of.

Using the Hit Rate as a Guide

Even after a team begins to close in on a 100% Hit Rate they still may show some occasional variance.  While intermittent variance is no cause for concern, a consistent pattern of moving away from the 100% line in a certain direction should raise your eyebrows.  If you're tracking your Hit Rate then this should be easy to spot before it gets away from you.  However, if you do find yourself in this situation then just refer to the Actual Velocity from your last few sprints.  You can use this number to reset the team back to a more reasonable forecast during your next Sprint Planning.  With the Hit Rate as a guide it won't take long to get back on track.

If You Must

Although metrics can be a helpful gauge of a team's progress, we should always remember that they're no replacement for simply getting to know your team and understanding the specific events surrounding each sprint.However, sometimes it's nice to have a guide that can call out areas where your team can still improve.  If you must use a metric, then Hit Rate is the one to look at.