# Teaching sampling with dragon data cards

## Data cards for teaching statistics

Data cards are a wonderful way for students to get a feel for data. As a University lecturer in the 1990s, I found that students often didn’t understand about the multivariate nature of data. This may well be an artifact of the kind of statistics they studied at school, which was univariate (finding the confidence interval for the mean of a set of numbers) or bivariate at best. And back then, when statistical analysis was done by hand calculation, this was all you could expect. How times have changed!

At the NZAMT (NZ Association of Mathematics Teachers) conference in 2015, both Dick de Veaux and Rob Gould suggested in their keynote addresses that students need to be exposed to multivariate data. Rob endorsed the use of data cards to enable this. Data cards are a wonderful tool for all levels of learning. In the New Zealand “Figure it out” series, there are several lessons that use data cards, generally made by the students themselves. We were inspired by this and have developed a set of 240 data cards with information about dragons, to help teachers and students learn and be successful in their statistical endeavours. In an earlier post I discuss the pros and cons of fictional data.

The Dragonistics data cards are now available to purchase, and we have a range of supporting materials for lessons and activities at various levels. You can find out more about data cards by clicking on this link.

## Teaching Sampling using Dragonistics data cards

A small sample of Dragonistics data cards

The real advantage of using data cards to teach sampling is that it is difficult, and approaching prohibitive, to record and analyse all the information. When you have a spreadsheet of data on a computer, to take a sample is contrived and can confuse students. They wonder why you would not simply analyse all the data for the population.Physically collecting data can take more time than is practical. With the data cards, we know we cannot easily process the data from all 240 or 480 dragons (depending on how many boxes you use.) Sampling then becomes a sensible solution. Different groups of students take different samples, and perform their own analysis, leading to similar, but not identical results. This shows the concept of variation due to sampling in a concrete and memorable way.

Some decades ago I developed a set of counters of four different colours, with data with different means and standard deviations. I used these to teach about the concept of sampling, and the students did ANOVA analysis on them to see if the means of the four groups were the same. This was a good way to teach this principle. However there were two limitations. The first limitation is that the data is not multivariate. There are just two

The old technology – two variables, and no embedded context

variables, colour and the number. And the second limitation is that there was no context. I made up a context to go with it, something around sales I think, as this was for an MBA class, which partly overcame that problem.

I’d like to think that I have learned from all the reading, research, experience, seminars etc on how to teach statistics that I have participated in. Consequently, were I to teach an MBA Quantitative methods class again, I think I would use the Dragon data cards. We have recently produced this lesson plan, that teaches about the concept of sampling and variation due to sampling. Dragon data cards could also be used for teaching about the mechanics of sampling, such as stratification and systematic sampling. There needs to be a story behind the analysis or there is no point to the conclusion. In the lesson previously alluded to, the scenario is that we are building separate shelters for male and female dragons, and it would be useful to have an idea of the relative strengths of male and female dragons.

## Evidence and Distribution

Using data cards gives a wonderful opportunity to explore the concepts of evidence and of distribution. The students lay out their cards in a nice bar chart arrangement, and say, “See  – there is a difference.” Teachers should then ask for evidence. Students need to be able to articulate what evidence there is for the effect they have observed, and place it in context. We have found this to be a useful process when teaching students of all levels.

With regard to distribution, if we work only with numbers, and find the medians of the two groups and observe that the median is higher for one group than the other, this is rather limited information. By observing the distribution of the dragon cards between the two sexes, we can see that there is overlap. It is not a clearcut difference. Additionally we may observe other effects, such as due to colour, which we might like to explore further in another journey around the Statistical Enquiry Cycle.

## Data cards are a win

It is fascinating that the concept of data cards is so new. It seems like an obvious idea, and makes concrete some very tricky abstract ideas. Data cards are useful at almost any level of understanding. As the need for understanding of statistics grows, there has been an emphasis on finding out better ways to teach for understanding. Clearly data cards are a win!

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I love to teach just about anything. My specialties are statistics and operations research. I have insider knowledge on Autism through my family. I have a lovely husband, two grown-up sons, a fabulous daughter-in-law and an adorable grandson. I have several blogs - Learn and Teach Statistics, and Building a Statistics Learning Community, are the main ones.