1. Insert name of presentation on Master Slide HCAI Charts HCAI Information for Action, November 2010 Presenter: Mari Morgan, Wendy Harrison

2. Insert name of presentation on Master Slide Types of Chart Rates with Confidence Limits Box & Whisker Plots Pareto Charts Run Charts Statistical Process Control Charts Funnel Plots Number between Events Chart

3. Insert name of presentation on Master Slide Rates with Confidence Limits From HPS Surveillance of Surgical Site Infection - Report for procedures carried out from 1 April 2002 - 30 June 2007

4. Insert name of presentation on Master Slide Rates with Confidence Limits The rate calculated is an estimate based on a particular sample. When further samples are taken, different estimates of the rate will be calculated. A confidence interval generates an upper and lower limit to the estimate of the rate. It gives an indication of how much uncertainty there is in our estimate of the true rate. The smaller the confidence limits, the more precise is the estimate of the rate. Wide confidence limits may indicate that more data should be collected before anything definite can be implied about the rate. Usually expressed as 95% confidence limits. Can construct this type of graph in Excel (Format Data Series – Y Error Bars)

5. Insert name of presentation on Master Slide Box & Whisker Plots (Boxplots) From: HPA Surveillance of HAI Report 2008

6. Insert name of presentation on Master Slide Box & Whisker Plots From: Wilson et al 2008. ICHE 29:219-226

7. Insert name of presentation on Master Slide Box & Whisker Plots From: HPS Surveillance of surgical site infection - Report for procedures carried out from 1 April 2002 - 30 June 2007

8. Insert name of presentation on Master Slide Box & Whisker Plots Useful way of displaying differences between groups of numerical data Based on 5 number summaries for each group: usually median, 25 th percentile, 75 th percentile, lowest observation and highest observation These statistics can be calculated in Excel using median, quartile, min and max functions.

9. Insert name of presentation on Master Slide Box & Whisker Plots Can use different summary statistics so need to always read the title for these plots The spacings between the different parts of the box help indicate the degree of spread and skewness in the data Can be used to indicate which observations are outliers Can be drawn vertically or horizontally No Box & Whisker Plot function in Excel, although it can be done.

10. Insert name of presentation on Master Slide Pareto Charts From: HPS S. aureus bacteraemias report – July 2008

11. Insert name of presentation on Master Slide Pareto Charts Originally used to describe the “80-20 rule” which says that 20% of the population controls 80% of the wealth Descending bar chart plotting the frequency of an event by category combined with a line chart giving the cumulative percentage of the total that each category represents. Can be created in Excel. Displays relative significance of different categories to a problem. Allows focus on categories that would have the greatest impact.

12. Insert name of presentation on Master Slide Run Charts From: HPS S. aureus bacteraemias report – July 2008

13. Insert name of presentation on Master Slide Run Charts

14. Insert name of presentation on Master Slide Run Charts A running record of a process over time Used to distinguish special cause from common variation Can be used for any process and any type of data eg measurements, counts, percentages, ratios Time measurement is on the x-axis and the process being measured is on the y-axis The centre line is generally the median value for the process.

15. Insert name of presentation on Master Slide Run Charts Looking for Special Cause Variation A run is 1 or more data points on the same side of the median. Can have a single point or many Analyse the runs to look for special cause variation: 3 tests 1.Too much/too little variability: - Need 16-25 data points on chart - Count the number of runs - Compare the number of runs for the number of data points you have in a table to assess whether variation is normal

16. Insert name of presentation on Master Slide Run Charts 2. Shift in Process: Special cause variation if runs contain too many data points For ≥20 data points, a run of ≥8 data points is too long For <20 data points, a run of 7 is also too long 3. Trend in Process: An unusually long series of consecutive increases or decreases in the data – at least 6 or 7 data points

17. Insert name of presentation on Master Slide Statistical Process Control Charts

18. Insert name of presentation on Master Slide Statistical Process Control Charts Hospital Monthly Surgical Site Infection Rate following C-Section, 01/01/2007 - 31/12/2007

19. Insert name of presentation on Master Slide SPC Charts Another way of distinguishing special cause from common variation More complex than run charts (MRI scan compared to x-ray) but more sensitive Several types – which used depends on type of data Upper and lower control limits are calculated and plotted SPC charts can be created in Excel

20. Insert name of presentation on Master Slide SPC Charts Types of SPC Chart Depends on type of data you have: 1 observation per time point Is the data count data? - Whole numbers only, counted not measured on a scale (eg no of defects) Yes → c chart No: Is the data measurement data? -Different values on continuous scale eg time, money, length, weight, volume Yes Does the measurement data have an increasing or decreasing trend? No → XmR (I) Chart Yes → XmR Trend Chart

21. Insert name of presentation on Master Slide SPC Charts 2. Numerator and denominator for each time point Are defects counted as Yes/No? Numerator is proportion of denominator and cannot be greater than denom (eg No of HAI infected patients – each patient only counted once regardless of no. of infections they have) Yes → P chart (if denom is variable )or np chart (if denom is constant) No: Are total numbers of defects counted? Possible for numerator to be greater than denom (eg total number of HAI infections, could be >than no of patients examined because of multiple infections in 1 patient) Yes → U chart

22. Insert name of presentation on Master Slide SPC Charts 3. Multiple observations of measurement data for each time point >5 observations for each time point or variable no of observations → S chart (XbarS) – examines variation within each time point Up to 5 observations for each time point → X-bar chart (XbarR) – examines variation between time points

23. Insert name of presentation on Master Slide SPC Charts Recognising Special Cause Variation Need 20-25 data points Single point outside control limits 2 out of 3 successive points above/below 2 SD line > 8 successive points on same side of centre line > 6 successive values increasing or decreasing

24. Insert name of presentation on Master Slide Funnel Plots Wilson et al 2008. ICHE 29:219-226

25. Insert name of presentation on Master Slide Funnel Plots HPS Review of Clostridium difficile Associated Disease Cases and Mortality in all Acute Hospitals in Scotland from December 2007 - May 2008

26. Insert name of presentation on Master Slide Funnel Plots HPS Review of Clostridium difficile Associated Disease Cases and Mortality in all Acute Hospitals in Scotland from December 2007 - May 2008

27. Insert name of presentation on Master Slide Funnel Plots HPS Surveillance of surgical site infection - Report for procedures carried out from 1 April 2002 - 30 June 2007

28. Insert name of presentation on Master Slide Funnel Plots Form of control chart often used for visual display of institutional performance Avoids ranking institutions Also used for comparing studies within a meta- analysis Scatter plot of performance measure vs sample size, with control limits imposed Control limits based on target for performance measure eg national average or expected reduction or acceptable threshold

29. Insert name of presentation on Master Slide Funnel Plots Control limits are 95% (2 SD) and 99% (3 SD) Construction of control limits depends on distribution of underlying data eg normal, binomial, poisson etc Can be constructed in Excel As sample size decreases, observation must be further from the target (eg national average) to be considered significantly different

30. Insert name of presentation on Master Slide Number Between Events Charts JC Benneyan, 2001. Healthcare Management Science 4, 304-318

31. Insert name of presentation on Master Slide Number Between Events Charts Number of C-Section Procedures between Infections for Hospital for 01/01/2008 - 31/03/2008 HospitalNumber of procedures preceding infection Date of Procedure with Infection 0 01/01/2008 1515/01/2008 0 318/01/2008 0 221/01/2008 0 325/01/2008

32. Insert name of presentation on Master Slide Number Between Events Charts When event is rare, ordinary control charts become long series of zero values with occasional occurrence of single events. As no. of events being controlled decreases, ordinary control charts lose effectiveness. Also may be more convenient to plot no. procedures or no. days between occurrence of events – easy to calculate, can plot in real time.

33. Insert name of presentation on Master Slide Number Between Events Charts Can construct control limits to detect special cause variation g-type charts Decrease in number of cases between infections corresponds to increase in infection rate therefore: –Upper Control Limits indicate where to investigate ‘what went right’ in the system (eg high no of procs before infection) –Often no Lower Control Limits – if event is rare the LCL is negative