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Analysing 2x2 Tables: Chi-Square Test and Beyond

  • 9:30am to 5pm
  • 1 day
  • 23 Feb 2023

Overview

This short course aims to demystify the range of statistics that can be used to summarise the associations between two binary variables.

It'll move beyond standard chi-square tests to investigate other options that may yield more useful information. 

This course is run by UCL's Centre for Applied Statistics Courses (CASC), part of the UCL Great Ormond Street Institute of Child Health (ICH).

Course content

When faced with exploring the relationship between two binary variables (e.g. comparing the percentage who test positive between two treatment groups, or between two subgroups such as males and females) it's common to display this as a 2x2 table and use a chi-square test to determine the statistical significance of any difference. Chi-square tests are commonly used to compare the percentage of individuals in two groups who share a trait.

However, there are many other statistics that may be applied to a 2x2 table to provide more useful information.

This course aims to help guide researchers through alternative analyses to decide on the most appropriate investigation of their data.

The following tests and concepts are covered in the course:

  • Fishers exact testing
  • Absolute risk reduction (ARR)
  • Proportions tests
  • Number needed to treat (NNT)
  • Relative risk (RR)
  • Attributable risk (AR)
  • Odds ratio (OR)
  • Kappa
  • Sensitivity and specificity
  • Positive and negative predictive values
  • Likelihood ratios

For each statistic we consider the interpretation and appropriate usages.

    Who this course is for

    The course is for non statisticians and is open to anyone who needs to understand or analyse 2x2 tables.

    Knowledge of the very basics of statistics (such as means, standard deviation, confidence intervals, etc.) is beneficial.

    Learning outcomes

    By the end of this course you should be able to:

    • understand what a chi-square significance test actually shows
    • understand the difference between chi-square and Fishers exact test, ARRs and NNT
    • understand the relative measures (RR, AR and OR)
    • know how to assess agreement for a 2x2 table
    • understand diagnostic statistics and their application
    • be better equipped to determine the best test to use for a 2x2 table

    Cost and concessions

    The fees are as follows:

    • External delegates (non UCL) - £125
    • UCL staff, students, alumni - £62.50*
    • ICH/GOSH staff and doctoral students - free    

    * valid UCL email address and/or UCL alumni number required upon registration

    Certificates

    You can request a certificate of attendance for this course once you've completed it. Please send your request to ich.statscou@ucl.ac.uk

    Include the following in your email:

    • the name of the completed course for which you'd like a certificate
    • how you'd like your name presented on the certificate (if the name/format differs from the details you gave during registration)

    Cancellations

    Read the cancellation policy for this course on the ICH website. Please send all cancellation requests directly to the course administrator

    Find out about other statistics courses

    CASC's stats courses are for anyone requiring an understanding of research methodology and statistical analyses. The courses will allow non-statisticians to interpret published research and/or undertake their own research studies.

    Find out more about CASC's full range of statistics courses, and the continuing statistics training scheme (book six one-day courses and get a seventh free.) 

    Course team

    Dr Catalina Rivera Suarez

    Dr Catalina Rivera Suarez

    Catalina has been an Associate Lecturer (Teaching) at CASC since January 2021. She has a PhD in Psychology and an MSc in Applied Statistics from Indiana University. She’s passionate about teaching courses in research methods, statistics, and statistical software. Catalina’s research focuses on studying how caregivers support the development of children's attentional control and language. She implements multilevel modeling techniques to investigate the moment-to-moment dynamics of shared joint visual engagement, as well as the quality of the language input, influencing infant learning and sustained attention at multiple timescales.

    Dr Manolis Bagkeris

    Dr Manolis Bagkeris

    Manolis has a BSc in Statistics and Actuarial-Financial Mathematics from the University of the Aegean and an MSc in Medical Statistics from the Athens University of Economics and Business (AUEB). He’s worked as a research assistant at University of Crete, UCL and Imperial College London. He’s been working at CASC since November 2021, providing short courses in research methods and statistics for people who want to develop or enhance their knowledge in interpreting and undertaking their own research. His interests include paediatric epidemiology, clinical and population health, HIV, mental health and development. He was awarded a PhD from UCL in 2021 on the topic of frailty, falls, bone mineral density and fractures among HIV-positive and HIV-negative controls in England and Ireland.

    Learner reviews

    "Thank you, as ever, for running another great course!"

    "Excellent, very clear presentation with the right amount of exercises in between, very useful."

    Course information last modified: 30 Nov 2022, 16:01