1. P-Chart
Farrokh Alemi, Ph.D.

2. Purpose To analyze adverse outcomes
Mortality
Infection rate
Medication error
To examine percent population with a characteristic
Percent satisfied with care
Percent diabetes under control

3. Assumptions Dichotomous, mutually exclusive and exhaustive events
The observations over time are independent
Case mix does not change over time
Sample represent population

4. Steps in Construction of Limits
p = total adverse events / total cases
si2 = p * (1-p) / ni
UCL = p + 3 * s
LCL = p – 3 * s
Plot, interpret & distribute
Number of cases in time period i

5. Example data

6. Calculate Grand Average p
=C10/B10
=SUM(C2:C9)
=SUM(B2:B9)

7. Calculate Standard Deviation
=(($B$12*(1-B$12))/B2)^0.5

8. Calculate Control Limits
= $B$12 + 3*E2
Reset negative numbers to zero

9. Plot chart

10. Interpret chart & distribute
Note control limits change because number of cases per time period changes
Any point outside the limits cannot be due to chance
No points fall outside the limits