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# Sample-Size Estimation and Power Calculations

• 5 hours
• 1 day
• 9 Oct 2019

## Overview

This one-day course covers the basics of sample-size estimation, including both precision and power estimation approaches.

It's likely to be useful to those embarking on a research project, or trying to complete ethics and grant application forms.

You'll have the opportunity to carry out practical workshop exercises using Excel sheets (computers are provided or you can bring your own laptop).

This course is delivered by UCL's Centre for Applied Statistics Courses (CASC) - part of the UCL Great Ormond Street Institute of Child Health (ICH).

## Course content

You'll be introduced to the concepts of sample-size estimation, including when and why this might be necessary.

Formulae are presented and discussed. You'll be given online access to a series of excel sheets which are pre-programmed to allow you to use the formulae.

In the morning the precision-based approach to estimating sample size is introduced, whereby the numbers are selected to produce a confidence interval for the relevant estimate with a specified width.

In the afternoon we progress to the more traditional power calculations which aim to give the sample required to determine a specified difference with selected power and significance levels.

All terminology will be explained as it's introduced in the sessions.

Sample-size estimation is discussed for the following measurements:

• Means
• Proportions/ percentages
• Time-to-event data
• Rates
• Measures of agreement
• Centiles

## Who this course is for

The course is open to anyone who wants to learn about the basics of estimating sample size.

Knowledge of the very basics of statistics (such as means, standard deviation, confidence intervals, etc.) is beneficial.

## Practical exercises and computers

The workshop will take place in a computer room where you'll have the opportunity to use the computers provided to gain full benefit from the practical exercises that use the excel sheets.

Alternatively, you're welcome to bring your own laptop if you prefer.

## Learning outcomes

By the end of this course you should be able to:

• understand why sample-size calculation is important prior to starting a study
• recognise and understand the two different types of sample-size estimation - precision and power
• understand the components required for sample-size calculation and how to estimate these
• undertake sample-size calculation using the online excel sheets
• adjust for unbalanced sample sizes in two groups
• recognise and appropriately adjust for non-independent outcome measures

## Cost and concessions

The fees are as follows:

• External delegates (non UCL) - £175
• UCL staff, students, alumni - £87.50*
• ICH/GOSH staff and students - free

* valid UCL email address and/or UCL alumni number required upon registration

Prices include printed course materials, refreshments (and lunch for non-ICH  participants).

## Certificates

You can request a certificate of attendance for this course once you've completed it. Please send your request to ich.statscou@ucl.ac.uk

Include the following in your email:

• the name of the completed course for which you'd like a certificate
• how you'd like your name presented on the certificate (if the name/format differs from the details you gave during registration)

## Cancellations

We accept cancellations up to five working days before the start of the course with a full refund, though we'd appreciate as much notice as possible to re-allocate the place. Places cancelled or changed after this point won't be eligible for a refund. Please send all cancellation requests directly to the course administrator.

## Find out about other statistics courses

CASC's stats courses are for anyone requiring an understanding of research methodology and statistical analyses. The courses will allow non-statisticians to interpret published research and/or undertake their own research studies.

Find out more about CASC's full range of statistics courses, and the continuing statistics training scheme (book six one-day courses and get a seventh free.)

## Course team

Angie, Director of the Centre for Applied Statistics Courses (CASC), has been involved in the provision of statistical training to medically based non-statisticians for 25 years. She has a first class Bachelor’s degree in Mathematics and a Master's degree in Applied Statistics from UCL, and a PhD Statistics in the development of likelihood based models for the construction of covariate-related centiles. She joined GOS ICH in 1990, began the development of CASC in 2008 and was ICH’s first teaching professor. She's an active member of local teaching committees, previously chaired an MSc examination board and is currently a member of the UCL Academic Board Education Committee.

Learner reviews

"Very well-run courses at an affordable price."

"The teacher was excellent!"

"Very interesting and informative. Materials distributed remain highly useful."

"Very good course, definitely useful and [the] spreadsheets provided are very handy."