I Chart

Picture of Kerrie Preston

Published on 9 August 2018 at 14:58

by Kerrie Preston

I chart
I charts are used for variable (continuous) data i.e. time, money, height/weight, temperature, workload/throughput/efficiency. It can also be used to record measures for each observed unit (e.g. individual weight per patient seen in a service). An I chart is not suitable for things you count (rather than measure); e.g. number of falls, incidents of violence, pressure ulcers.


 Typical instances in healthcare would be:

  • Waiting times (e.g. Time taken between referral to first assessment)
  • Money (e.g. cost of successive admissions)
  • Average Weight
  • Blood Pressure


I Chart Example

Here we will show you what data is required when creating an I Chart and how this is reflected in the Chart itself. 


So lets say the 'Aim' of the project was to:

Reduce the proportion of patients with pressure sores by 50% in six months.

and the measure was:

Average length of hospital stay.


You would need to capture the following data:

Time Period Dates when the value was recorded (Daily, Weekly, Monthly).
Value The measurements collected at every time period.


Data Capture Example:

Average length of hospital stay

I Chart Data Example

I Control Chart Example:
Average length of hospital stay



 I Chart

If you want to learn more about SPC then take a look at our


Struggling to create your I Chart in Excel? Visit Life QI!



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