--- title: Hypothesis Testing Example - Pfizer Atrial Fibrillation Research - Survival Analysis description: Hypothesis Testing Example - Use nQuery and learn how to calculate sample size and use a power analysis calculator for clinical trials. This example focuses on Pfizer Atrial Fibrillation Research. image: https://www.statsols.com/hubfs/Master_Images/___HeroBannerImages/nQuery%20Sample%20Size%20Software%20Image.png --- Explore the Scientific R&D Platform ![Top Bar background texture](https://flow-cytometry.net/wp-content/uploads/2024/07/nav-bg.png) ![](https://flow-cytometry.net/wp-content/uploads/2024/07/Luma-TM.png) Scientific intelligence platform for AI-powered data management and workflow automation [Explore Luma   ](https://www.dotmatics.com/luma-data-management-platform) [![Prism logo](https://flow-cytometry.net/wp-content/uploads/2024/07/Prism-Logo-White-2.png) Statistical analysis and graphing software for scientists ](https://www.graphpad.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![Geneious logo](https://flow-cytometry.net/wp-content/uploads/2024/07/Geneious-Logo-White-2.png) Bioinformatics, cloning, and antibody discovery software ](https://www.geneious.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![SnapGene logo](https://cdn.labarchives.com/assets/16.23.0/assets/images/dotmatics/lab-archives/top-bar/PreNav-Logo-SnapGene.svg) Plan, visualize, & document core molecular biology procedures ](https://www.snapgene.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![Protein Metrics logo](https://cdn.labarchives.com/assets/16.23.0/assets/images/dotmatics/lab-archives/top-bar/PreNav-Logo-Protein-Metrics.svg) Proteomics software for analysis of mass spec data ](https://proteinmetrics.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![LabArchives logo](https://flow-cytometry.net/wp-content/uploads/2024/07/LabArchives-Logo-White-2.png) Electronic Lab Notebook to organize, search and share data ](https://www.labarchives.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![OMIQ logo](https://cdn.labarchives.com/assets/16.23.0/assets/images/dotmatics/lab-archives/top-bar/PreNav-Logo-OMIQ.svg) Modern cytometry analysis platform ](https://www.omiq.ai/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![FCS Express logo](https://cdn.labarchives.com/assets/16.23.0/assets/images/dotmatics/lab-archives/top-bar/PreNav-Logo-FCS-Express.svg) Analysis, statistics, graphing and reporting of flow cytometry data ](https://denovosoftware.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![Easy Panel logo](https://flow-cytometry.net/wp-content/uploads/2024/07/EasyPanel-Logo-White-2.png) Intelligent panel design & inventory management for flow cytometry ](https://flow-cytometry.net/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![nQuery logo](https://cdn.labarchives.com/assets/16.23.0/assets/images/dotmatics/lab-archives/top-bar/PreNav-Logo-nQuery.svg) Software to optimize designs of clinical trials ](https://www.statsols.com/) [![M-Star logo](https://flow-cytometry.net/wp-content/uploads/2024/07/M-Star-Logo-White-2.png) Computational fluid dynamics (CFD) software for engineers and researchers ](https://www.mstarcfd.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [![SoftGenetics logo](https://flow-cytometry.net/wp-content/uploads/2024/07/SoftGenetics-Logo-White-2.png) Genetic analysis software for research, forensics & healthcare applications ](https://softgenetics.com/?utm_medium=referral&utm_source=nquery&utm_campaign=dotmatics-top-bar) [Explore the Scientific Software   ](https://www.dotmatics.com/portfolio) [![nQuery Logo](https://www.statsols.com/hubfs/nQuery%20Logo.svg "nQuery Logo")](https://www.statsols.com/) [![Pricing](https://no-cache.hubspot.com/cta/default/488764/23ddd076-07af-4f0a-9388-5a58a5369002.png)](https://cta-redirect.hubspot.com/cta/redirect/488764/23ddd076-07af-4f0a-9388-5a58a5369002) [![Free Trial](https://no-cache.hubspot.com/cta/default/488764/93ddde0f-93b2-4893-a3db-0523d2334739.png)](https://cta-redirect.hubspot.com/cta/redirect/488764/93ddde0f-93b2-4893-a3db-0523d2334739) # Sample Size Determination Example ## AREA: Survival Analysis | Cardiology ![nQuery In Use Background Web Opacity 35](https://www.statsols.com/hs-fs/hubfs/Master_Images/___HeroBannerImages/nQuery%20In%20Use%20Background%20Web%20%20Opacity%2035.png?width=1920&name=nQuery%20In%20Use%20Background%20Web%20%20Opacity%2035.png "nQuery In Use Background Web Opacity 35") #### Pfizer Atrial Fibrillation Research #### Title: Apixaban versus Warfarin in Patients with Atrial Fibrillation **Objective: **In this randomized, double-blind trial, we compared apixaban (at a dose of 5mg twice daily) with warfarin (target international normalized ratio, 2.0 to 3.0) in 18,201 patients with atrial fibrillation and at least one additional risk factor for stroke. The primary outcome was ischemic or hemorrhagic stroke or systemic embolism. The trial was designed to test for noninferiority, with key secondary objectives of testing for superiority with respect to the primary outcome and to the rates of major bleeding and death from any cause. **Year:** 2011 **Source:** New England Journal of Medicine **Link: ** [http://www.nejm.org/doi/full/10.1056/NEJMoa1107039](http://www.nejm.org/doi/full/10.1056/NEJMoa1107039) **Clinical Area: **Cardiology | **Sample Size Section in Paper/Protocol:** | | --- | | ''The primary non inferiority hypothesis required that apixaban preserve at least 50% of the relative reduction in the risk of stroke or systemic embolism associated with warfarin (62%) in six previous, major randomized, controlled trials.10 This hypothesis provided a lower 95% confidence interval of 1.88 for the relative risk with placebo as compared with warfarin, and one half of this value was 1.44 (or 1.38 on a log scale). We estimated that with the occurrence of the primary outcome in 448 patients, the study would have 90% power to ensure that the upper boundary of the 99% confidence interval for the relative risk would be less than 1.44 and that the upper boundary of the 95% confidence interval for the relative risk would be less than 1.38, on the assumption that apixaban and warfarin had identical effects. On the basis of the overall event rate during the trial, we planned to recruit 18,000 patients in order to reach this number of events with approximately 2 years of follow-up.” |   **From Protocol: Incidence rate = **1.2 events per hundred person-years **Average Follow-up = **2.1 years  |** Expected Dropout** = 1% ***Note:**** Only the 99% confidence interval with 1.44 relative risk analysis replicated since protocol states this was analysis with higher sample size.* **Summary of Necessary Parameter Estimates for Sample Size Calculation:** |  Parameter | Value | | --- | --- | |  Significance Level (1-Sided) | 0.005 | |  Non-Inferiority Margin | 1.44 | |  Power | 90% | |  Incidence Rate per Year | 0.012 | |  Average Follow-Up (Years) | 2.1% | | Expected Dropout | 1% | #### **Email me this example in PDF format** **Step 1: ** Select the **Non-inferiority test for Two Exponential Survival Curves** from the Select Test Design & Goal window. This can be done **using the radio buttons** or alternatively, you can** use the search bar** at the end of the Select Test Design & Goal window. ![Sample Size Calculator Example- nQuery- Example 20- Img 01- Non-inferiority test for Two Exponential Survival Curves](https://www.statsols.com/hs-fs/hubfs/Master_Images/___PageImages/Worked%20Examples/nQuery%20Example%20Images/Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2001-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png?width=579&name=Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2001-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png) **Step 2:** Enter the parameter values for sample size calculation taken from the study protocol **![Sample Size Calculator Example- nQuery- Example 20- Img 02- Non-inferiority test for Two Exponential Survival Curves](https://www.statsols.com/hs-fs/hubfs/Master_Images/___PageImages/Worked%20Examples/nQuery%20Example%20Images/Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2002-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png?width=575&name=Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2002-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png)** **Step 3: **Once Power is entered, sample size is calculated automatically. | This gives a number of events of 448, as per the study protocol. | | --- |   **![Sample Size Calculator Example- nQuery- Example 20- Img 03- Non-inferiority test for Two Exponential Survival Curves](https://www.statsols.com/hs-fs/hubfs/Master_Images/___PageImages/Worked%20Examples/nQuery%20Example%20Images/Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2003-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png?width=512&name=Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2003-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png)** **Step 4: **Calculate the sample size based on the number of events, the incidence rate and the average follow up period. ![Sample Size Calculator Example- nQuery- Example 20- Img 04- Non-inferiority test for Two Exponential Survival Curves](https://www.statsols.com/hs-fs/hubfs/Master_Images/___PageImages/Worked%20Examples/nQuery%20Example%20Images/Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2004-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png?width=512&name=Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2004-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png) Adjust sample size for 1% dropout rate ![Sample Size Calculator Example- nQuery- Example 20- Img 05- Non-inferiority test for Two Exponential Survival Curves](https://www.statsols.com/hs-fs/hubfs/Master_Images/___PageImages/Worked%20Examples/nQuery%20Example%20Images/Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2005-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png?width=613&name=Sample%20Size%20Calculator%20Example-%20nQuery-%20Example%2020-%20Img%2005-%20Non-inferiority%20test%20for%20Two%20Exponential%20Survival%20Curves.png) | **This gives approximately 18000 as per the protocol** | | --- |   #### **Email me this example in PDF format** ### Free 14 Day Trial ![Demo Icon white](https://www.statsols.com/hs-fs/hubfs/Demo%20Icon%20white.png?width=330&name=Demo%20Icon%20white.png) **No download required**   [Try Now](https://www.statsols.com/nquery-demo) ##### **LOCATION** GraphPad Software DBA Statistical Solutions, 225 Franklin St FL 26 Boston, MA, 02110-2853, United States Copyright © Statsols. 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