P-Chart Farrokh Alemi, Ph.D.

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

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

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

Example data

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

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

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

Plot chart

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