Ask more, know more, do more

Do They Really Want a Coffee Maker?

Do They Really Want a Coffee Maker?

The center of any scientific endeavor typically features two smaller questions; a) are these two groups different and b) how would we know if any differences we observe are actually real? For example, if group A has a mean of 2.6 on a five point scale of interest in having a coffee maker in the office and group B has a mean of 3.2, we observe a difference.  But, how can we be sure that group B wants a coffee maker more than group A?  In other words, do we have enough statistical power to be sure about our conclusions?  How much data does one need?  The answer depends on the size of the effect we observe—smaller effects need more data points to illuminate stable group differences.

When conducting an experiment, for example, and wish to compare groups on a factor, such as gender, for example, you typically need at least 25 people per “cell.”  That is, 25 people in each level of the variable of interest. So for gender you’d need 25 men and 25 women.  If you want to compare men and women’s level of education (and there were four levels of education), then you’d need 200 respondents —4 (education) X 2 (gender) X 25. So when you introduce other variables into your model, it causes the required responses to rise.

There is a nifty power calculator here, courtesy of the University of Dusseldorf, for folks that want to check it out.  Tell us what you think.

Tags: , ,

2 thoughts on “Do They Really Want a Coffee Maker?

  1. Coffee Maker says:

    It doesn’t seem relevant as to how much these groups want a coffee maker. Surely, they both should get one and all have the opportunity to enjoy a really good cup of coffee. I think I’ll go and make one now!

Leave a Reply

Your email address will not be published. Required fields are marked *

Inspired? Create your own survey.

Make your own survey

Sign In

Sign up to get started

PRO Sign Up 
Sign Up FREE

Latest Features

Curious about what we’ve been working on?

View New Features

Get expert survey help

Get expert survey help


Best practices for planning expert surveys

Planning makes writing your survey easy.

Download eGuide

How many responses do you need?

Use our sample size calculator to find out!

Calculate now

Analyze survey data like a pro

Learn to slice and dice data using the Analyze tool.

Download eGuide