Label group boxes: Title each box with the group name, followed by “(n = x)”. Replace x with the number of patients, samples or animals included in that group at that phase of the study. If your group name doesn’t clearly describe your unit of observation, describe your unit of observation after “(n = x)” (example: n = x Sprague Dawley rats).
Don’t forget to label the first box and include the sample size. If your first stage is about screening and observations haven’t been assigned to groups yet, the group name should specify the population studied (e.g. “Bl6 mice (n = 50)”, “healthy pregnant women, <12 weeks gestation (n = 79)”.
Group names should clearly specify what was done to the group, or inclusion criteria for the group. Avoid vague names like “Group 1”, “Control group”, “Case group” or “Treatment group.”
The “units” should clearly specify what was observed. Replace vague terms like “animals” or “participants” with more specific terms like “Sprague Dawley rats”, “brain slices from Bl6 mice”, or “healthy men and women”.
Don’t use the term “patients”. This term can refer to humans in clinical studies, or animals in veterinary studies.
Specify sex or gender: After showing the total sample size, consider presenting a breakdown by sex or gender. Example: n = 12 Sprague Dawley rats (6 M, 6 F).
Avoid abbreviations when possible. They make the flow chart hard to read and different abbreviations mean different things in different fields.
If your experimental unit differs from the number of participants, samples, or animals assessed, specify this. Instead of “(n = x)”, write (N = x experimental units, n = x individuals). Replace the words “experimental unit” and “individual” with specific terms for your study.
Example: Doctor’s offices were randomized to treatment or placebo. All patients within the practice were assigned to the same group. Describe your sample size as “(N = 10 practices, n = 5,623 patients).”
Example: You start by harvesting cells from human participants. You then conduct studies on cultured cells. At the sample collection phase, your units may be “n = 5 patients”. At later phases, your units may be “n = 5 6-well plates.”