David Dubins, Ph.D., B.A.Sc.
Associate Professor, Teaching Stream
Leslie Dan Faculty of Pharmacy
144 College Street
Toronto, Ontario
M5S 3M2
Lab Website: http://phm.utoronto.ca/pharmlab

My Tiny Contribution to Clinical Research: FARTSSIE.

Hi, I used to work in clinical research, specifically in clinical trial design and analysis. I love working things out on my own. It's often the best way to understand a phenomena. Sample size calculation is one of those finicky niche areas that require precise calculations using expensive statistical packages. I thought I would develop a free tool to estimate sample sizes, largely based on equations from the following reference:

Julious, SA. "Tutorial in Biostatistics - Sample sizes for clinical trials with Normal data."
Statist. Med. (2004); 23:1921–1986.

I've created an Excel spreadsheet that utilizes the equations in a Microsoft Excel workbook, which arrives at the same sample sizes assoftware packages such as SAS, NQuery, and PASS. The Excel workbook is called "Free Analysis Research Tool for Sample Size Iterative Estimation".

To download the latest version of FARTSSIE, click the following link:

Download FARTSSIE23.xlsm

I now use this spreadsheet in my bioequivalence electives at the Leslie Dan Faculty of Pharmacy, University of Toronto.

Visit Dr. Russel Lenth's Website, the person who made this software possible.

  • Version 2.2: Release Date 1-Feb-17
    • Added Lehr's Formula to Superiority, Parallel worksheet
  • Version 2.2: Release Date 1-Feb-17
    • Added ±d values to graphs, adjusted BE limits for replicate designs
  • Version 2.1: Release Date 16-Jan-17
    • Added distribution graphs to most spreadsheets
  • Version 2.0: Release Date 11-Jan-17
    • TPD HIghly Variable Drug BE limit calculation added
  • Version 1.9:
    • FDA sigmaw0 changed to 0.294, EMA widened CI limits constrained to 69.84-143.19%
  • Version 1.8:
    • Fixed precision of ISV and ratio for BE sheets
    • Updated to .xlsm format
  • Version 1.7:
    • Calculate Sample Sizes for Reference-Scaled BE Approaches, for FDA and EMEA ("Bioequivalence Replicate" spreadsheet)
  • Version 1.6:
    • "ScaledBE - HVD" worksheet added based on the proposed FDA approach for scaled bioequivalence limits at the 06 October 2006 meeting of the Advisory Committee for Pharmaceutical Sciences (ACPS)
    • Alternate approaches for expansion of BE limits also included:
      • Expansion of BE limits based on fixed sample size
      • Widening of BE limits based on reference variability (3 approaches)
      • Expansion of BE limits based on fixed sample size and scaling
  • Version 1.5:
    • "Calculate Power" button added to Bioequivalence worksheets
  • Version 1.4:
    • Now compatible with Excel 2007
    • No extra library to install
    • Opt-out warning at 1001 subjects
    • Bioequivalence warning if expected ratio isn't within BE limits
  • FARTSSIE calculates sample sizes for the following clinical trial designs:
    • Superiority Trials: Parallel and 2-way Crossover
    • Clinical Equivalence Trials: Parallel and 2-way Crossover
    • Non-Inferiority Trials: Parallel and 2-way Crossover
    • Bioequivalence Trials: Crossover, Replicate, and Parallel
    • Trials to a Given Precision: Parallel and Crossover
    • Difference Between Proportions (for smaller trials, up to 170 subjects)
    • Variance Correction (baseline correction, post-dose measures correction, or both)
  • A "boss button" on most trial designs which will work backwards from the sample size your boss (or client) wants.
  • No annoying advertisements, registration options, or guarantees. 

I hope you find this tool useful. Did it work? Is there something you liked or disliked about it? Do you have a suggestion that could make it better? Your feedback is appreciated.

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Last Updated: 12-Jul-18