[Guide] What to look for in a sample size calculator. This guide examines the most important factors you need to know when deciding what software to use for this important part of your study.
Using a sample size calculator to determine the appropriate sample size is a crucial step in study design. A study that has a sample size which is too small may produce inconclusive results and be considered unethical. Similarly, a study that has a sample size which is too large will waste scarce resources and could expose more participants than necessary to any related risk.
So what do you look for in a sample size calculator? Below we have listed the most important factors you need to know when deciding what software to use for this important part of your study.
Different Clinical Trial Objectives:Equivalence
Sample Sizes For Different Types of Data:
The data is continuous and assumed to follow a bell curve, centred at the mean and with the spread determined by the standard deviation.
The responses can only take on two possible states - usually related to success/ failure or yes/no. The data is summarised using proportions.
The data is discrete and takes on natural, ordered categories where the distance between each category is not known.
Clinical Trial Designs
Randomized Clinical Trials
Subjects are randomized to a treatment or control, such as a placebo.
Sample Size Statement for Regulatory Submission
This communicates the method and parameters used to calculate the sample size needed for the clinical trial.
Some methods, such as odds ratio tests, can be adjusted for multiple covariates.
Analyzing the dependence of the sample size or power on specific parameters in the study.
Bayesian Sample Size
Using prior knowledge about a parameter to better estimate the probability of success of a trial.
Adaptive Designs for Efficacy
Sample size can be re-estimated in an adaptive trial depending on the probability of finding for efficacy.
Provision can be made in a study to stop for futility, if there is early evidence that the study will not find for efficacy.
Sample Size Re-Estimation
Sample size can be updated during the study to account for a changed variability or treatment effect.