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Calculating Power and Sample Size

Overview:

Learn the theory, the logic, and the steps to calculate power and sample sizes so you can easily get started on your research project.

Every granting agency and many committees require sample size and power estimates before funding a study.

But most statistics classes don't teach you how to calculate them. Sure, maybe for one-sample t-tests, if anything, but not for the real kinds of statistics you need to actually use.

Mainstream statistical software makes it easy to calculate power after the fact, which is dubious, at best, and prone to misinterpretation.

This 3-hour workshop will get you up to speed on the meaning and logic of power, sample size, and how to calculate them. We'll start with a review, from the beginning, of what power means and how it relates to the statistical tests, effect sizes, standard deviations, and sample size.

You will learn how to calculate simple sample estimates using two types of specialized software (one free and one commercial).
Format:
Webinar live online workshop

Webinars are a fabulous way to learn. You get all the advantages of a live workshop without the disadvantages.

I will be conducting the workshop live. You attend over the internet as you see what is happening on my computer screen. Audio is through either your computer speakers/microphone or by telephone. Webinars are highly interactive--see the presentation on my screen, ask questions out loud or write it into the chat--yet you never have to leave your house or office. 

Save on travel expenses and fit it into your regular schedule. And because you’re not travelling, we don’t have to concentrate an overwhelming amount of information into one or two days. We can spread it out in digestible amounts.

And best of all, unlike live workshops, the presentations will be recorded. You will get the audio and video recording from every session, so if you can't make that time, or need to review the material in a few months, you’ll have it forever to review at your own convenience.

 
What You Will Learn:

 
You will learn:
  • A review of power, effect sizes, hypothesis tests, and Type I and Type II errors

  • How power, effect size, and standard deviation relate to sample size in a variety of statistical tests--including t-test, ANOVAs, linear and logistic regressions

  • The logic of sample size calculations, so you can apply it to any problem

  • The five pieces of information you need to do any sample size calculation and where to get them

  • Your options for increasing power in a study

  • The importance of effect sizes to power and sample size calcuations and the best way to measure them in a variety of tests

  • Why it really isn't useful to do power calculations after running a study

  • Where sample size calculations fit into the eleven steps of data analysis

  • How to do simple sample size calculations using a free online calculator

  • How to do more complex calculations using StudySize 2.0 Software

  • Examples of prospective sample size estimates for a two sample t-test, and ANOVA, a multiple regression, and a logistic regression analysis
Who Is It For:
This workshop is for you if you:
  • Need to calculate sample size estimates for grant proposals, dissertation proposals, or just want to be able to make sure a research study is worth doing.

  • Will be writing a dissertation proposal this semester

  • Learned the basics of power and sample size in statistics class, but never really how to do them in real research situations or in anything harder than a t-test

  • Have a statistical consultant available to help you calculate sample sizes, but need to understand what pieces of information to hand over to her or him and how to get that information.

Prerequisites:

  • You will get the most out of the workshop if you have had at least two statistics classes and experience in data analysis.

You do not need experience in any specific statistical software. We will be using two pieces of software--a free online java applet and StudySize 2.0. You can get a free 3-week trial download of StudySize 2.0, which I recommend you do just before the workshop. I will send instructions at the time.

 
What's Included:
  • One three-hour workshop session. This session will contain a presentation and time for questions.  You will hear me and see exactly what is happening on my screen.

  • A bonus 60-minute Question & Answer session. Just your questions and my answers. This is two weeks later, so you have a chance to try things out on your own data, then come back with questions. It's when you try things out on your own data, then have any questions cleared up, that you cement your learning.

  • Video Recordings of the workshop and Q&A session made available within 48 hours. So you can review the material right away, a year later, or while doing the exercises. Or if you need to miss the live sessions, you can still participate on your own schedule.

  • PDF handouts of the presentation slides, which will be available ahead of time, on which you can take notes.

  • Access to our central Workshop Basecamp. This is a secure web-based location where you can post questions between sessions, get call-in information for each webinar session, and download handouts and recordings.

  • You are encouraged to ask questions about calculating your own sample size estimates in addition to general questions about the topic.  (But please keep questions to the topic of the workshop so that they’re useful for everyone). 

  • Homework.  (Yes, homework!).  It’s optional, but you’ll get more out of the workshop if you participate fully by doing homework.  If you get stuck, ask a question in the Q&A session or on our message board.
The Instructor:

Karen Grace-Martin, the workshop instructor and founder of The Analysis Factor, is a professional statistical consultant with masters degrees in both applied statistics and social psychology.  Her own career started in psychology research, where her frustration in applying statistics to her data led her to learn more statistics. 

Karen was a professional statistical consultant at Cornell University for seven years before founding The Analysis Factor.  She has guided and trained researchers through their statistical analysis for over 15 years. Her focus is on helping statistics practitioners gain an intuitive understanding of how statistics is applied to real data in research studies.
Registration Fee:

This workshop has ended. If you'd like a notice when the next session is scheduled in Fall 2010, please fill in your name and email address below.

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Free Bonuses

Everyone will receive two free bonus recordings:

1. A 60 minute Audio Presentation: The 11 Steps to Performing Any Statistical Model

All statistical modeling--whether ANOVA, Multiple Regression, Poisson Regression, Multilevel Model--is about understanding the relationship between independent and dependent variables. The content differs, but as a data analyst, you need to follow the same 11 steps to complete your modeling.

This audio will give you an overview of these 11 steps:

  • what they are
  • why each one is important
  • the general order in which to do them
  • on which steps the different types of modeling differ and where they're the same

Understanding the steps will make your modeling more efficient and keep you on track.

2. A 60-minute Video Presentation: The First 3 Steps to Statistical Modeling: How to Clarify the Research Question, the Design, and the Variables

All statistical modeling--whether ANOVA, Multiple Regression, Poisson Regression, Multilevel Model--is about understanding the relationship between independent and dependent variables. The first 3 steps in modeling set up the entire rest of the analysis.

1. Write out research questions in theoretical and operational terms

2. Design the study or define the design

3. Choose the variables for answering research questions and determine their level of measurement

It is the way you do these three steps that determines the rest of the analysis. Doing them explicitly and doing them well can save you days of time and endless frustration.

 
Optional Extras

1. For those of you who want a written reference to refer to, the option to purchase a companion ebook based on the transcripts of the workshop will be available for an additional $25.00.

2. A one hour one-on-one folllow-up consultation with Karen Grace-Martin at a 40% discount: $60. Get specific help on your project. Must be used within 30 days of the workshop. Limit 2 hours per person.

 
Refund Policy

Your registration fee is fully refundable up to 72 hours in advance minus a $15 administration fee. Because enrollment is limited, no refunds will be granted after the program begins.

That said, your satisfaction is guaranteed. If you participate in the full workshop and find you are not satisfied for any reason, we will give you a full refund. Just notify us within 90 days of the conclusion of the program.