G*Power is free software that provides an effective user-friendly solution for power analysis as part of the routine statistical data analysis procedure.

G*Power was developed at the Institute for Experimental Psychology in Dusseldorf Germany and was designed as a general stand-alone power analysis program for statistical tests. It offers a wide variety of calculations related to power analysis along with graphics and protocol statement outputs.

How G*Power is used

Power analysis is commonly used in disciplines such as:

  • agriculture
  • animal studies
  • health science
  • social and behavioural research

The power of any test of statistical significance is defined as the probability that it will reject a false null hypothesis. Alternatively, the statistical power is defined as the probability of NOT committing a Type II error (which does not reject the null hypothesis when it is false). Power analysis is normally conducted before the data collection. Statistical power analysis helps researchers determine the smallest sample size that is suitable to detect the effect of a given test at the desired level of significance. It involves several statistical concepts and the power analysis formula is very model specific.

Types of analysis

G*Power3.1 offers 5 different types of statistical power analysis:

  1. A priori (sample size N is computed as a function of power level 1 − β, significance level α, and the to be detected population effect size)
  2. Compromise (both α and 1 − β are computed as functions of effect size, N, and an error probability ratio q = β/α)
  3. Criterion (α and the associated decision criterion are computed as a function of 1− β, the effect size, and N)
  4. Post-hoc (1− β is computed as a function of α, the population effect size, and N)
  5. Sensitivity (population effect size is computed as a function of α, 1 − β, and N)

G*Power workshop

The QCU runs this one day hands-on practical workshop on request from CSU researchers (HDR students and staff members). The workshop is run face-to-face and requires a minimum of 2 participants, with a maximum of 10. We are flexible in running this workshop multiple times and on different campus as demand requires.

Structure of the workshop

The workshop runs for 5 hours, divided into three sessions as follows:

  • 9:30am – 10am: Registration and morning tea
  • 10am – 12pm: Learning and practice session 1 – install the GPower software onto laptop computers; Basic concepts of statistical power analysis; First touch with GPower; Applying GPower to perform power analysis for five different statistical models.
  • 12pm – 1pm: Lunch
  • 1pm – 2:30pm: Learning and practice session 2 – Learn and practise power analysis for six more statistical models including the ANOVA model with more than two categorical factors.
  • 2:30pm – 3pm: Afternoon tea
  • 3pm - 4:30pm: Learning and practice session 3 – Learn and practise power analysis for five more statistical models including a simple repeated measure regression model case.
  • 4:30pm: Close

Cost of the workshop

The registration fee is $100 per person and includes a working lunch. This helps ensure people who register will commit their time to participate.

How to register

Please send us your expression of interest by:

  • emailing John at gxie@csu.edu.au
  • talking to us about your needs by phone: 02 6933 2229 (John)