PPT-Power and Sample Size: Why Should We Care?

November 17 2015 Allen Kunselman MA Division of Biostatistics and Bioinformatics Department of Public H ealth Sciences Quotes An approximate answer to the right question is worth a good deal more than an exact answer to the wrong question. Study Design and Sample Size. Ideally we are involved in a study from the beginning. As statisticians (an epidemiologist) part of our role is to ensure the study is designed to address the primary hypothesis under consideration. Jed Friedman, World . Bank. SIEF Regional Impact Evaluation Workshop. Beijing, China. July 2009. Adapted from slides by Esther . Duflo. , J-PAL. Planning Sample Size for . Randomized Evaluations. General question: . PSY505. Spring term, 2012. April . 11, . 2012. Today’s Class. Power Analysis. Statistical Power. Power Analysis. A set of methods for determining. The probability that you will obtain a statistically significant result, assuming a true effect size and sample size of a certain magnitude. ipdpower. in designing a randomised cluster study of an oral health intervention in care homes. David Boniface (UCL). d.boniface@ucl.ac.uk. . Robert. . McCormick. . (Kent). Alexis Zander (Kent). . Biostatistics, AZ. MV, CTH. May 2011. Lecture 6. Power and Sample Size in Linear Mixed Effects Models. 1. . Date. Date. Name, department. 2. . Outline of lecture 6. Generalities. Power and sample size under linear mixed model assumption. Laura . Chioda. World Bank. 1. Outline. Ingredients of a general recipe called “Statistical Sampling Theory” . Key message. : a successful design involves some guess work. It is important to have a general rule, but then needs discussion depending on the case at hand. +. Principles of Simulation. Benjamin Neale. March 4. th. , 2010 . International Twin Workshop, Boulder, CO. Slide of Questions. What is power?. What affects power?. How do we calculate power?. What is simulation?. and . Sample size considerations. Methods in Clinical Cancer Research. March 3, 2015. Sample Size and Power. The most common reason statisticians get contacted. Sample size is contingent on design, analysis plan, and outcome. General Sampling Issues. Thinking of the steps in sampling (from theoretical population to respondents)—what are some biases that can come in at each point?. What is the proximity similarity model? What are issues with that model?. Review of Type I & Type II Errors. When we conduct a test of any hypothesis regardless of the test used we make one of two possible decisions:. Reject the null (H. o. ) in favor of the alternative (H. Office of Methodological & Data Sciences. November . 13, 2015. Sarah Schwartz. www.cehs.usu.edu/research/omds. Quantitative Research. Research Question. Clear, focused & concise question that drives the study. Sample 4. Females. 43% . Work on management positions. 14%. Variable One. 22%. Variable Two. 31%. Variable Three. 34%. Variable Four. 39%. Variable Five. 2 in 5. Additional Descriptive statistics. 80%. Plan. Review of hypothesis testing. Power and sample size . Basic concepts. Formulae for common study designs. Using the software. When should you think about power & sample size?. Start thinking about statistics when you are planning your study. : . Grant . Writing for Cancer Studies . Masha Kocherginsky, PhD. Professor of Biostatistics, Departments of Preventive Medicine. Director, Quantitative Data Sciences Core, Lurie Cancer Center. Northwestern University.