control charts: an overview -...

Control Charts: an overviewWilliam Peters

Improvement Coach Professional Development Program

Wave 3, Workshop 2

March 13th, 2017Day 1

Question 2 of the Model for Improvement

What are we trying toaccomplish?

How will we know that achange is an improvement?

What change can we make thatwill result in improvement?

Model for Improvement

PlanAct

DoStudy

Source: Associates for Process Improvement

The most basic

understanding of the

2nd question is this:

MEASUREMENT

Quality Improvement Fundamentals LLC

How Do We Know That a Change

is an Improvement?• Improvement is about testing and implementing change

within a system, not measurement!

The purpose of measuring is

to answer critical questions

and to guide intelligent action.


Distribution of Wait Times

0

10

20

30

40

50

60

5 15 25 35 45 55 65 75 85 95 105

Wait time (days) for Visit

nu

mb

er

of

vis

its

Clinic Wait Times > 30 days

0

2

4

6

8

10

12

14

16

C F G D A J H K B I L E

Clinic ID

# o

f w

ait

s >

30 d

ays

Relationship Between Long

Waits and Capacity

0

5

10

15

20

75 95Capacity Used

# w

ait

tim

es >

30 d

ays

Run Chart Shewhart Chart

Frequency Plot Pareto Chart Scatterplot

IH p. 8-34

There are several

tools we use in

improvement to

make sense of the

variation that is

inherent in EVERY

measure.How else would we do it? Make it up?!

Understanding variation in data

I know these! I DON’T know these!


before after

1 Improvement is the result of a change in the process

and gains are held …3

result is positive, relevant, meaningful …

2

on a measure that matters to the organization4

Cycle

time

We need data over time to show improvement

REAL SUSTAINABLE IMPROVEMENT

The biggest difference between Run

and Control Charts:

If you are using the Run Chart, you use:

a Run Chart

If you are using the Control Chart, you use:

… with special software


Differences between Run and Control Charts:

You need: Pencil and Paper or Excel Special Software ($1,200 -

$5,000)

Training: [you tell me, how hard is it?] Definitely more difficult

Who creates: Anyone, front-line safe ideally Specially trained software dude

Interpretation: [you tell me, how hard is it?] More difficult

Center Line: Median Mean

Sensitivity: Easily enough to get the job

done

More sensitive, more

sophisticated, more detail

Tests: 4, pretty easy to learn Dozens of sets, harder to learn

• Shift

• Trend

• Too many, too few runs

• Astronomical

Each one of these is a SET of rules

containing 4 to 8 different rules

How many:

Ideal use:

Data needed:

Cool Factor:


Differences between Run and Control Charts:

You need: Pencil and Paper or Excel Special Software ($1,200 -

$5,000)

Training: [you tell me, how hard is it?] Definitely more difficult

Who creates: Anyone, front-line safe ideally Specially trained software dude

Interpretation: [you tell me, how hard is it?] More difficult

Center Line: Median Mean

Sensitivity: Easily enough to get the job

done

More sensitive, more

sophisticated, more detail

Tests: 4, pretty easy to learn Dozens of sets, harder to learn

How many: THE run chart 7, depending on the measure

Ideal use: All improvement activities System dashboards

Data needed: At least 10 points, >= better At least 15 points, >= better

Cool Factor: “Impressive!” “Improvement Ninja”

Do by hand: 10-20 minutes? See you in your next life!


11

0

2

4

6

8

10

12

14

16

Number of Interruptions During Med Passes by Day

Oh look! A Run Chart!

Baseline median 11, extended over test

20 data points, 1 on median, 19 useful observations

10 Runs, at 19 points table shows btw 6 - 15

Begin Sterile

Cockpit test

almost a shift


Oh look! A CONTROL CHART!

“API” Rules that I use in healthcare

• Trend of 6 descending/ascending

• Shift of 8 above/below mean

• 2 of 3 beyond the second sigma

• Above/below upper/lower control limit

• 15 within the 1st sigma

Sigma zones

1

1

2

3

3

2

(RARE!)


Oh look! A CONTROL CHART!

“API” Rules that I use in healthcare

• Trend of 6 descending/ascending

• Shift of 8 above/below mean

• 2 of 3 beyond the second sigma

• Above/below upper/lower control limit

• 15 within the 1st sigma


Remember the “Astro” in the Run Chart?

Rule 4

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Me

as

ure

me

nt

or

Ch

ara

cte

ris

tic

Blatantly obvious that value is unusual. SMEs mostly agree


A control chart with UCL crossed

There is no argument here … these data are different!Quality Improvement Fundamentals LLC

It can get hairy …

Remember, I have to teach interpretation to CEO AND the BoD!!!

1 res. had 3 ED trips resulting in 2 admits (HB), 1

res. admitted after fall, 1 res.

admitted d/t unresponsive

episode

1 res. related to repertory distress

and expired, 1 fall, 2 related to

family insistence, 2 admitted with

illness

NICE!


The most complicated to grasp:

Individuals – Moving Range

SME interpretation: Stable since building addition. Op-Def: Total income from all sources of revenue all levels of

care.

New addition opened

with 13 nursing bedsFoundation Campaign

for the new bus started

The range chart: only interpret UCL/LCL violations!

If range chart is in control we hide it

In a control chart we can “ghost data points”

… IF reasonable and rational people can agree to our

reasoning!


Notice the “staggered limits” in this P Chart

The larger the denominator, the tighter the limits


The Control Chart Decision Tree

Variables Data Attributes Data

>1

observation

per

subgroup?

< 10

observations

per

subgroup?

X bar R X bar S XmR

Are the

subgroups of

equal size?

Is there an

equal area of

opportunity?

Occurrences

& Non-

occurrences?

np-chartp-chartu-chartc-chart

Decide on type

of data

Yes

YesYes

Yes

Yes No NoNo

No No


15.9

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

Percent All-Cause, 30 Day Readmissions

20 data points

8 runs 6/16

6 shift

But never forget …


point

I&P

or

I&E

&

LEARN

& TAKE

ACTION!

control charts: an overview -...

Documents