Statistical Process Control (SPC)

Summary

SPC charts are a useful tool for monitoring and reporting, allowing KPIs to be looked at over time and in the context of expected variation, moving away from some of the pitfalls of traditional RAG reporting and providing insights into trends and, if there is a target, whether it is likely to be reliably met.

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Tip

Find out more about the technique in the Atlas entry here.

The most popular solution for SPC charts in R is the NHSRplotthedots package.

You can find out more about the package in the Atlas entry here

Below is a sample code snippet that makes an SPC chart for a time series.

First, we import our NHS R plot the dots package.

In this case, rather than using real data, we’ll be using a sample dataset of ED attendances provided by the NHSRdatasets library package.

Now we’ll filter our dataset down to just one organisation, type 1 attendances only, and a shorter period of time.

We can take this subset of data and use the NHSRplotthedots library.

Note

Code Source: NHSR Plot the Dots Documentation @ https://nhsrplotthedots.nhsrcommunity.com/

Click here to view and copy the whole example

install.packages("NHSRplotthedots")
install.packages("NHSRdatasets")

library(NHSRdatasets)

library(NHSRplotthedots)
library(dplyr)

sub_set <- ae_attendances |>
  filter(org_code == "RQM", type == 1, period < as.Date("2018-04-01"))

sub_set |>
  NHSRplotthedots::ptd_spc(
    value_field = breaches,
    date_field = period,
    improvement_direction = "decrease"
  ) |>
  NHSRplotthedots::ptd_create_ggplot(
    y_axis_label = "4-hour wait breaches",
    main_title = "SPC of A&E waiting time breaches for RQM"
)

Warning

There is not currently an actively maintained, production-ready equivalent to the NHS R plot the dots programme.

One of the major benefits of the NHS-aligned packages are that they use the recognised , as well as ‘making data count’ defaults for values such as the number of points that are considered a run.

The Making Data Count Excel Templates

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