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Table 3 Levels of evidence for the AOTA Evidence-Based Practice Project

From: Safety and efficacy of tinea pedis and onychomycosis treatment in people with diabetes: a systematic review

Level

Definition

Design

I

Randomized trial: Comparison of two or more groups or conditions in an experiment with random assignment to group or to sequence of conditions in a repeated-measures design

II

Non-RCT: Comparison of two or more groups or treatments in a quasi-experiment without randomization to group, condition, or sequence

III

Non-RCT: Comparison of one group pre- and post-treatment

IV

Single-subject design: One subject measured at intervals throughout an intervention

N

A Narratives and case studies

Sample size

A

n ≥ 50 persons per condition or group or observations in a single subject design

B

n ≥ 20 persons per condition or group or observations in a single subject design

C

n < 20 persons per condition or group or observations in a single subject design

Internal validity

1

High internal validity: No strong alternate explanation for outcome or other threats to validity, such as attrition, unblinded evaluation, unequal treatment, or spontaneous recovery

2

Moderate internal validity: No strong alternate explanation for outcome but one or two threats to validity exist

3

Low internal validity: Does not meet criteria for 1 or 2

External validity

a

High external validity: Participants represent population and treatment represents current practice or has strong theoretical support and the research was done in a natural (home or clinic) setting

b

b Moderate external validity: Has two of the criteria listed for a

c

Low external validity: Has one or fewer criteria listed for a

  1. AOTA-American Occupational Therapy association; RCT-Randomised controlled trial. Figure taken from Tromblay and Ma [38]