Skip main navigation

New offer! Get 30% off your first 2 months of Unlimited Monthly. Start your subscription for just £35.99 £24.99. New subscribers only T&Cs apply

Find out more

SD Pros and Cons

.
16.7
Sometimes we can’t use the mean because we have too much skew or extreme scores. In those situations, the mean is meaningless, no pun intended. Go ahead and look at the example on the screen. Here, we have an extreme score up around 13, and as a result, our average for this set of numbers is above 4. Of course, the typical score is around 2 or 3, so clearly, the mean here is biassed or not useful. Well, the standard deviation is based on the mean. Remember? We find how far people differ from the mean. And in this case, we wouldn’t use the standard deviation either.
52.5
So as a general rule, when you can’t use the mean because of skew, you also can’t use the standard deviation. Shares all the same strengths and weaknesses of the mean. So in this case, we’re not going to use the standard deviation. We’re going to have to find an alternative measure. So in the next lesson, we’re going to develop an alternative or a backup to the standard deviation, just like we had to do for our averages.
This article is from the free online

Essential Mathematics for Data Analysis in Microsoft Excel

Created by
FutureLearn - Learning For Life

Reach your personal and professional goals

Unlock access to hundreds of expert online courses and degrees from top universities and educators to gain accredited qualifications and professional CV-building certificates.

Join over 18 million learners to launch, switch or build upon your career, all at your own pace, across a wide range of topic areas.

Start Learning now