ã Copyright ASQ. Following article was
published in Quality Progress Magazine, October 1997 Issue.
Continuous Improvement on the Free-Throw Line
by Timothy Clark and Andrew Clark
In 1924, Walter Shewhart developed an improved problem-solving to continually
improve quality by reducing variation (the difference between the ideal outcome
and the actual situation). To help guide improvement efforts, Shewhart outlined
a process referred to as the plan-do-study-act (PDSA) cycle. The PDSA cycle
combined with traditional concepts of decision-making and problem-solving, are
what my son and I used to continuously improve his basketball free-throw
shooting.
Recognizing the problem
Identify the facts. I had observed over a three-year period
(1991-1993), that in basketball games, my son Andrew’s free-throw shooting
percentage averaged between 45% to 50%.
Identify and Define The Process. Andrew’s process for shooting free
throws was simple: Go to the free-throw line, bounce the ball four times, aim
and shoot. The desired outcome was for a higher free throw shooting percentage.
An ideal outcome, or perfection, would be one in which 100% of the shots fall
through the middle of the rim, land at the same spot on the floor every time,
and roll straight back in the shooter’s direction after the landing.
Plot the points. To confirm my observations on the results of the
current process, we went to the YMCA and Andrew shot five sets of 10 free throws
for a total of 50 shots. His average was 42%. Results were recorded on a run
chart (see Figure 1). Based on this information as well as on past observations,
I estimated the process was stable.
Figure 1. Free-Throw Shooting Run Chart
Decision making
Identify the causes. Causes of variation in any process can be
identified through the general categories of people, equipment, materials,
methods, environment and measurement. A cause-and-effect diagram is used to
graphically illustrate the relationship between the effect-a low free throw
shooting percentage—and the principal causes (see Figure 2.).
Figure 2. Free-Throw Shooting Cause-and-Effect Diagram
In analyzing my son’s process, I noticed that he did not stand at the same
place at the free-throw line every time. I believed his inconsistent shooting
position effected the direction of the shot. If the shot goes left or right,
there is a smaller probability that the ball will have a lucky bounce and go in.
I also noticed that he didn’t seem to have a consistent focal point.
Develop, analyze and select alternatives. The alternatives selected
for Andrew, a right handed shooter, were for him to line up his right foot on
the middle of the free-throw line, focus on the middle of the front part of the
rim, and visualize the perfect shot before he released the ball. The modified
process is:
1. Stand at the center of the free-throw line.
2. Bounce the ball four times.
3. Focus on the middle of the front part of the rim, and visualize perfect
shot.
4. Shoot.
Develop an action plan. The course of action at this point was for
Andrew to shoot five more sets of 10 free throws to test the effectiveness of
the changes.
Problem solving
Implement the selected alternative and compare actual with expected
results.
The new process resulted in a 36% improvement in Andrew’s average
free-throw percentage at basketball practice, which raised his average to 57%.
(see Figure 3). The new process was first implemented in games towards the end
of the 1994 season, in the last three games, Andrew hit nine of his 13
free-throws for an average of 69%.
Figure 3. Free-Throw Shots Made Before and After
Implementing the PDSA Cycle (March 17, 1994 to
November 23, 1994)
During the 1995 season, Andrew made 37 of 52 free throws in games for an
average of 71%. In one extremely close game where the other team was forced to
foul Andrew’s team in an effort the get the ball back, Andrew made seven of
his seven shots, which helped his team win the game. In team practices, the
coaches had the players shoot two free throws and then rotate. For the entire
season, Andrew hit 101 of 169 of his team practice free throws for an average of
60%.
As we monitored Andrew’s process from March 17, 1994 to January 18, 1996,
we plotted the total number of practice shots made out of 50, using Shewhart’s
number-of-affected-units control chart (see Figure 4). A control chart is a
trend chart with upper and lower control limits. If all of the data points falls
within the control limits, the variation in the process is due to normal or
common causes of variation and the conclusion can be made that the process is
stable or predictable. In other words if you always do what you always did, on
average, you will usually get what you always got."
If any points fall outside the limits, the variation is due to a special
cause which makes the process unstable or unpredictable. A special cause might
represent a temporary or fleeting event and might require little or no action to
resolve. Variation due to a common cause requires a permanent change in the
process. In this case, the process is stable which will make it easier to
validate future improvement efforts.
Figure 4. Determining Whether the Free-Throw Process Is Stable
(March 17, 1994, to Jan. 18, 1996)
In the late summer of 1995, Andrew went to a basketball camp where he was
advised to change his shooting technique. This change to his process reduced his
shooting percentage during the 1996 season to 50%. This caused him to lose
confidence in his shooting ability, and consequently, he took fewer shots. We
then reinstalled his old process, and his shooting percentage returned to its
former level. In one series of 50 practice free throws, he hit 35 of 50 shots
for an average of 70% and in another set, he hit 32 of 50 for an average of 64%.
During the remaining team practices, Andrew hit 14 of 20 of his practice free
throws for an average of 70%. During the final three games, he hit two of three
free throws for an average of 67%.
During the 1996 and 1997 seasons, Andrew was a point guard and was
responsible for controlling and distributing the ball. In this position, he had
fewer opportunities to shoot free throws. Therefore, during the 1997 season, he
had the opportunity to shoot only 12 free throws but he made nine of them for an
average of 75%.
Overall Benefits. In addition to the tangible results, such as
improved free-throw shooting, the intangible benefits were also significant. For
example, Andrew’s confidence improved, and he learned how to determine when
changes to his shooting technique result in improvement. W. Edwards Deming
referred to this type of knowledge as profound.
Continuous Improvement
Take appropriate action based on the results of the study. In
preparation for the 1998 season, Andrew’s priorities for improvement are to
continue to monitor his free- throw shooting to ensure it remains stable and to
work on improving the shooting percentage for his two and three-point shots.
Knowledge changes how people look at the world
Shewhart’s methodology represents a problem-solving or decision-making
process that requires a fundamental change in thinking. Traditionally, people
are trained to make decisions based on gut feelings or on a relatively few
facts. The PDSA process requires people to first determine if the process
outcome is due to a common cause or a special cause. This knowledge becomes the
foundation for making decisions, which can only be developed by plotting points.
Developing a knowledge and understanding of variation will change the way you
look at the world forever and can lead to unprecedented levels of quality.
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