Confidence Intervals

Reviewed and revised 26 August 2015


Confidence intervals are the range around the sample mean within which you predict the means of the population to lie


  • using a standard normal distribution curve, 95% of the sample means should lie within 1.96 SE above and below the population mean. This the 95% CI for the population mean.
  • Standard Normal Distribution Curve: CI = sample mean +/- (z0.05 x SE)
  • T-test: CI = sample +/- (t0.05 x SE)


  • small sample
  • large variance within sample


  • precision of sample mean as an estimation of the population mean.
  • more information on significance of p-value.
  • allows clinical relevance to be made.
  • allows for graphical representation between several means.
  • if OR presented with CI and includes 1 -> there is no difference between the two groups.
  • if p value presented with CI that includes 0 -> there is no difference between the two groups.

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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