In my last column, I considered two of the most common questions faced by a statistical educator and the deeper questions that need to be addressed. I encouraged people to consider their everyday reality for the necessary context. Predictably, some become frustrated by my lack of concise answers and try to distract me by asking, “Well, even though I can’t think of a situation, how many data points do I need to have a good chart?”
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This predictable question is once again met by my predictably vague reply, “How much data do you have?” It’s usually not very much.
Despite the pedantic proclamations many of you have encountered in favor of waiting for anywhere from 15 to 25 data points, I have found that useful limits may be computed with much less data. As few as seven to 10 observations are sufficient to start computing limits, especially if it’s all you have—something that happens to me frequently. What else are you going to do? I dare you to find a more accurate way to assess the situation.
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Comments
Iterations
Hi Davis,
We're never trained to operate in the realm of uncertainty. All formal education focuses exclusively on certainty - well defined problems with closed-form solutions. Even our managers ask for one-button-solutions. Is it any wonder then that in the face of a real world problem we look for "the formula"; to plug-n-chug numbers to get the "right answer?" Most have us have never learned how to learn, so I think understand why people ask the types of questions they do. My exposure to the learning cycle (Plan-Do-Study-Act) came very late. It's very decent of folks like Dr. Donald Wheeler and you, among others, to suffer fools and patiently guide them in their journey of understanding.
New and experienced workers need to learn through experience guided by mentors the reality of uncertainty and how to minimize it using the learning cycle. Like you asked: When you don't have "enough" data "what else are you going to do?" You need to make the most of the data you have...until you get more, if you can get more. The only way to build confidence about your knowledge i.e. reducing uncertainty is by replicating results. There is no one question, therefore there is no one answer. You grow your knowledge about a process over time and through experimentation by deeply considering what you're observing. You have to expend brain energy.
Best regards,
Shrikant Kalegaonkar (Twitter: https://twitter.com/shrikale, Blog: http://shrikale.wordpress.com)
Thank you for your kind words and additional comments
There's really nothing more to be said. You've said it well. When we try to help people who are sincerely trying to learn and accept our challenges, they are hardly "fools." It's the arrogant "fools" who try their best to play "got'cha" with us for whom I have no patience. It's nice to have "colleagues" such as you joining us in our quality "journey."
Kind regards, Davis
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