Cited by 452Statistical Methods in Clinical TrialsStatistical Methods in EpidemiologyMeta-analysis and systematic reviews

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Sample Size Estimation in Clinical Research

Wang, Xiaofeng, Ji, Xinge·2020·Chest

DOI 10.1016/j.chest.2020.03.010

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Abstract

Sample size determination is an essential step in planning a clinical study. It is critical to understand that different study designs need different methods of sample size estimation. Although there is a vast literature discussing sample size estimation, incorrect or improper formulas continue to be applied. This article reviews basic statistical concepts in sample size estimation, discusses statistical considerations in the choice of a sample size for randomized controlled trials and observational studies, and provides strategies for reducing sample size when planning a study. To assist clinical researchers in performing sample size calculations, we have developed an online calculator for common clinical study designs. The calculator is available at http://riskcalc.org:3838/samplesize/. Finally, we offer our recommendations on reporting sample size determination in clinical studies.

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Shunmugam, D., Shanmugam, S., Manoharan, K., & Gandhi, A. (2025) · Cancer Research, Statistics, and Treatment · doi:10.4103/crst.crst_228_24
Urinary Neutrophil Gelatinase-Associated Lipocalin Level is Associated with the Incidence of Postoperative Acute Kidney Injury: An Observational Study
Parami, P., Senapathi, T., Duarsa, G. W. K., Wande, N., Martadiani, E. D., Arif, S. K., Chandra, S., & Widjanarko, S. D. (2025) · Bali Journal of Anesthesiology · doi:10.4103/bjoa.bjoa_77_25
Assessment and Comparison of Tribal and Nontribal Pregnant Women’s Oral Health Status and Dental Attendance in Salem District, Tamil Nadu – A Comparative Study
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Qizhu Yuling prescription in the prevention of postoperative metastasis and recurrence of esophagus cancer: study protocol for a randomized, double-blind, placebo-controlled, multicenter clinical trial
Kong, M., Xu, B., Zhu, G.-H., Wang, X.-M., Kuang, Z., Sun, Q., Liu, K.-X., Wang, Z., Zhang, Y., & Li, J. (2025) · Frontiers in Oncology · doi:10.3389/fonc.2025.1478390
Self-citation
Evaluation of Functional Capacity and Pulmonary Functions in Pediatric Patients With Chronic Kidney Disease: A Retrospective Study.
Çavuşoğlu, I., Safran, E., & Yavuz, S. (2025) · Pediatric Exercise Science · doi:10.1123/pes.2024-0128
Prevalence and predictors of stunting in children and adolescents aged 1-18 years with nephrotic syndrome attending Mulago Hospital, Uganda
Nalubega, R., Batte, A., & Kiguli, S. (2025) · BMC Nephrology · doi:10.1186/s12882-025-04025-2
“Assuming 95% confidence interval and error within 5% and using Kish Leslie [21] sample size formula; n= (Z 2* p(1-p)/d 2 .”
Post-Implantation Syndrome Incidence After Secondary Endovascular Aortic Interventions
Ribeiro, T., Ferreira, R., Amaral, C., Gonçalves, F., & Ferreira, M. E. (2025) · EJVES Vascular Forum · doi:10.1016/j.ejvsvf.2025.02.005
Irritation Test of Cream Preparations Made from Purple Cabbage Extract Against Healthy Skin Using The Path Test Method
Deswani, D., Djuwitaningsih, S., Cartika, H., & Malau, P. (2024) · JURNAL INFO KESEHATAN · doi:10.31965/infokes.vol22.iss4.1458
“The number of volunteers in this study met the level of sample representativeness based on the minimum requirements for phase 1 clinical trials (Wang, & Ji, 2020).”
Translation and Psychometric Evaluation of the Chinese Version of the Gynecological Cancers Awareness Scale.
Tian, X.-J., Yang, L., Liu, Y., Feng, L., Wang, R., & Li, Y. (2024) · Journal of Obstetric, Gynecologic and Neonatal Nursing · doi:10.1016/j.jogn.2024.10.005
Seroprevalence of Hepatitis B Virus in Pregnant Women and Associated Risk Factors, Monitored at the Yaounde University Teaching Hospital, Cameroon
André, M.-M., Carole, S., Jacky, N.-B., & Honorine, R. (2024) · International Journal of Biomedical Engineering and Clinical Science · doi:10.11648/j.ijbecs.20241002.11
Efficacy of the intravenous formulation of fentanyl citrate administered orally as premedication in paediatric patients undergoing open cardiac surgery
Elbardan, I. M., Shehab, A. S., Yacout, A. G., & Mabrouk, I. (2024) · Journal of Perioperative Practice · doi:10.1177/17504589241301311
“…was required to be 90% sure that the upper limit of a one-sided 95% confidence interval (CI; or equivalently a 90% two-sided CI) would reject a difference of more than 24% (non-inferiority margin) on the side of the midazolam group (Blackwelder 1982, Sealed Envelope Ltd. 2012, Wang & Ji 2020).”
Femoroacetabular Impingement Morphological Changes in Sample of Patients Living in Southern Mexico Using Tomographic Angle Measures
Cárdenas-Dajdaj, R., Flores-Rivera, A., Rivero-Peraza, M., & Méndez-Domínguez, N. (2024) · Tomography · doi:10.3390/tomography10120141
Kajian Penulisan Surat Keterangan Kematian di Rumah Sakit 'XYZ'
Sasongko, P. P., & Herianto, I. (2024) · Action Research Literate · doi:10.46799/arl.v8i11.2356
“Data yang digunakan adalah data sekunder yaitu data yang terdapat pada salinan yang terdapat di lembar ketiga rincian sebab kematian Sertifikat Medis Penyebab Kematian (SMPK) / Surat Keterangan Kematian di RSPAD Gatot Soebroto dalam periode Tahun 2023 (12 bulan).”
Effectiveness of integrating an Ayurvedic protocol to lifestyle modifications in reducing cardiovascular disease risk: A hospital-based randomized trial
Rani, R. K. R., & Raj, R. (2024) · Journal of Research in Ayurvedic Sciences · doi:10.4103/jras.jras_326_23
Comparing the Clinical Effectiveness of High-Dose and Low-Dose Statin Therapy in Patients with Atherosclerotic Coronary Artery Disease (CAD)
Ghafoor, A., Rehman, T. U., Sarfaraz, M., Rind, A., Nasir, A., Khan, J., & Shahzad, S. (2024) · Pakistan journal of health sciences · doi:10.54393/pjhs.v5i10.1993
Comment on dose-response relationship between awake prone-positioning duration and PaO2/FiO2 changes and risk of disease aggravation in patients with severe COVID-19.
Daungsupawong, H., & Wiwanitkit, V. (2024) · Australian Critical Care · doi:10.1016/j.aucc.2024.09.007
Psychotherapeutic Effect of Listening to Quran Recitation on Dental Anxiety: A Randomized Controlled Trial
Alattar, A. N., & Hamzah, B. F. (2024) · Dental Hypotheses · doi:10.4103/denthyp.denthyp_124_23
How to Determine When Your Sample Size Is Big Enough But Not Too Big
Siedlecki, S. (2024) · Clinical nurse specialist CNS · doi:10.1097/nur.0000000000000844
Accuracy study of Angiotensin 1-7 composite index test to predict pulmonary fibrosis and guide treatment.
Vos, N. D., Bruyneel, M., Roman, A., Antoine, M., Bruyneel, A., Alard, S., André, S., Dahma, H., Chirumberro, A., & Cotton, F. (2024) · Clinica chimica acta; international journal of clinical chemistry · doi:10.1016/j.cca.2024.119926
Anti-SARS-CoV-2 Antibodies versus Vaccination Status in CAD Patients with COVID-19: A Prospective, Propensity Score-Matched Cohort Study
Mink, S., Drexel, H., Leiherer, A., Cadamuro, J., Hitzl, W., Frick, M., Reimann, P., Saely, C., & Fraunberger, P. (2024) · Vaccines · doi:10.3390/vaccines12080855
“Sample size calculation was conducted for cohort studies with dichotomous outcomes and independent proportions [27,28] with correction for continuity [27].”
Method
Letter to the Editor about “Tamsulosin 0.8 mg daily dose in management of BPH patients with failed tamsulosin 0.4 mg monotherapy and unfit for surgical intervention”
Qiang, Y., Zhang, Q., Feng, Y., & Cao, Q. (2024) · World journal of urology · doi:10.1007/s00345-024-05106-x
BESS: A Bayesian Estimator of Sample Size
Bi, D.-H., & Ji, Y. (2024) · doi:10.48550/arxiv.2404.07923
“A comprehensive review can be found in Wang and Ji [2020].”
Background
Development of a Multiplatform Tool for the Prevention of Prevalent Mental Health Pathologies in Adults: Protocol for a Randomized Control Trial
Ramos, N., Besoaín, F., Cancino, N., Gallardo, I., Albornoz, P. D., Fresno, A., Spencer, R., Schott, S., Núñez, D., Salgado, C., et al. (2024) · JMIR Research Protocols · doi:10.2196/52324
Reply to Dr. Yang et al.
Uslu, Y., Aydal, P., & Ulus, B. (2023) · Journal of Perianesthesia Nursing · doi:10.1016/j.jopan.2023.08.009
Study protocol for a preliminary optimization trial of transcutaneous electrical acupoint stimulation device simulating acupuncture Deqi
Mu, J.-D., Zhang, Z., Ma, L.-X., Li, H., Huang, X.-S., Li, X., Qian, X., Ma, L.-H., Zhang, Q.-Y., & Sun, T.-Y. (2023) · European Journal of Integrative Medicine · doi:10.1016/j.eujim.2023.102296
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Cua-Lim, J. T., Lim, W., & Chua, A. (2023) · Journal of Laryngology and Voice · doi:10.4103/jlv.jlv_2_23
Patterns and outcomes of cardiovascular complications among adult patients with chronic kidney diseases attending Benjamin Mkapa Hospital in Dodoma, Tanzania A protocol of a prospective longitudinal study.
Mbalazi, M., Meremo, A., Alphonce, B., & Meda, J. (2023) · medRxiv · doi:10.1101/2023.06.15.23291478
Predictors and outcomes of cardiac dyssynchrony among patients with heart failure attending Benjamin Mkapa Hospital in Dodoma, central Tanzania: A protocol of prospective-longitudinal study
Bilikundi, P., Alphonce, B., Nyundo, A., & Meda, J. (2023) · medRxiv · doi:10.1371/journal.pone.0287813
“Sample size estimation In order to estimate the sample size, the proportionate formula used in prospective cohort studies will be used[19]”
Method
Factors that Influence Innovation Acceptance on Bioactive Paper for Fruit Shelf Life Extension
Hengboriboon, L., Sookman, A., Khamdee, P., Phengtham, T., & Gebsombat, N. (2023) · 2023 International Conference on Innovation, Knowledge, and Management (ICIKM) · doi:10.1109/icikm59709.2023.00009
“A purposive sample size procedure was used to determine which entrepreneurs and consumers with innovative adoption factors would be tested for innovation bioactive in this study [19].”
Method
Seroprevalence of hepatitis C virus antigen in patients with chronic liver disease and hepatocellular carcinoma at 12th week of treatment: a cross-sectional study
Mbaga, D., Bikoï, J. N., Okobalemba, E. A., Essindi, J., Mikangue, C., Membangbi, A., Ngoutane, A., Elang, A., Touangnou-Chamda, S. A., Sake, C., et al. (2022) · The Pan African Medical Journal · doi:10.11604/pamj.2022.43.72.35450
Application of Structural Equation Model-Partial Least Square for Factors Affecting the Risk of Pesticide Poisoning
Muslim, A. S., Dadang, D., Indrasti, N. S., & Syaukat, Y. (2022) · Jurnal Aisyah Jurnal Ilmu Kesehatan · doi:10.30604/jika.v7i1.939
“…of population exposed to pesticides (P = 0.566) D = Absolute precision (number of people that must be included in the sample so that prevalence can be exceptional within 15% (0.15) above and below the true prevalence with a level of 95% confidence (Charan & Biswas, 2013 ; (X. Wang & Ji, 2020) .”
BackgroundInfluential
Response: Commentary: Statistical Modeling for the Prediction of Infectious Disease Dissemination With Special Reference to COVID-19 Spread
Yadav, S. K., & Akhter, Y. (2022) · Frontiers in Public Health · doi:10.3389/fpubh.2021.783201
Comparison of Different Obesity Indices associated with Type 2 Diabetes Mellitus Among Different Sex and Age Groups in ChinaPreprint
Ge, Q.-W., Li, M., Xu, Z., Qi, Z., Zheng, H.-Y., Cao, Y., Huang, H., Duan, X., & Zhuang, X. (2021) · Research Square · doi:10.21203/rs.3.rs-154511/v1
“In that study, the cut-off value for WHR was not suitable for predicting T2DM compared with those of BMI and WHtR [19].”
Method
Development of a Prediction Model for Severe Intraventricular Hemorrhage in Moderate-to-Late Preterm Infants
Zhang, W.-Q. (2026) · Advances in Clinical Medicine · doi:10.12677/acm.2026.162727
Assessing the feasibility of an education intervention for triage interruption management
Johnson, K., Wagner, R., Guan, T., Barbosa, S. D. F. F., & Sasangohar, F. (2026) · Acta Paulista de Enfermagem · doi:10.37689/acta-ape/2026ao2013
Assessing the feasibility of an education intervention for triage interruption management
Johnson, K. D., Wagner, R., Guan, T.-Y., Barbosa, S. D. F. F., & Sasangohar, F. (2026) · Acta Paulista de Enfermagem · doi:10.37689/acta-ape/2026ao2013i
Fall prevention self-management behavior and associated factors among community-dwelling older adults in China: A cross-sectional study
Yao, M., Yang, Y.-T., Yang, Y.-W., Ye, Q., Chen, Q., & Lin, T. (2025) · Nursing Communications · doi:10.53388/in2025021
“According to Kendall’s experience with estimating sample size for multiple linear regression, the sample size should be 10 to 20 times the number of variables [22, 23].”

Authors: Wang, X., & Ji, X.
Affiliations: Cleveland Clinic (US)
Corresponding author: Wang, Xiaofeng
ORCID: Wang, Xiaofeng
Venue: Chest
Publisher: Elsevier BV
Published: 2020-07
Volume: 158
Issue: 1
Pages: S12-S20
ISSN: 0012-3692 (ISSN-L)
DOI: 10.1016/j.chest.2020.03.010
OpenAlex: W3039422431
Cited by: 452
References: 0
Citations by year: 2026: 87 · 2025: 105 · 2024: 121 · 2023: 76 · 2022: 36 · 2021: 22 · 2020: 4
FWCI: 24.19
Type: journal article
Language: en
Open access: closed
Licence: www.elsevier.com/tdm/userlicense/1.0/ (tdm)
www.elsevier.com/legal/tdmrep-license (tdm)
Locations: CHEST Journal (publishedVersion)
PubMed (publishedVersion)
Topics: Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Clinical Trials
Physical Sciences › Mathematics › Statistics and Probability › Statistical Methods in Epidemiology
Social Sciences › Decision Sciences › Statistics, Probability and Uncertainty › Meta-analysis and systematic reviews
Keywords: sample size determination, randomized controlled trials, observational studies, clinical research design, statistical power
MeSH terms: Humans, Research Design, Randomized Controlled Trials as Topic, Sample Size, Observational Studies as Topic

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