# PegStats

## 3D model description

PegStats is a system to help students explore statistical concepts. The pegs contain numbers on the surface. The distribution of the numbers on the pegs is set by what you print. The students can draw pegs from the set you printed and create easy histograms of the population by sliding the pegs into the included tray. PegStats can be used from elementary school through college. Obviously histograms are easily taught, but it also works for bimodal populations, the effects of filtering, and the inadequacies of mean to describe a population. Even ANOVA can be used on the populations. The students can also use the numbers on the pegs (recording them as they select them) to perform statistical calculations from mean through proving the distribution is normal. I've included a PDF file (PegStats Details) with some lesson ideas. This math manipulative actually mimics an activity I did in my first college chemical engineering lab (we used resistors instead of pegs) so the learners can scale to quite an advanced level.

Using the Power of 3D printing, the Customizer can be used to make trays which go higher than 8 if your printer bed is large enough. The enclosed OpenScad file can be used to make distributions with averages from -9 to 99 (or more if want to change the font size).

## 3D printing settings

Print a tray to create the histograms. You can use a low fill since it has plenty of strength from the walls. Pick a peg distribution set. They are labeled as such "a" is the average and "s" is the standard distribution. All the sets are designed not to go below 1 or over 8. The averages and standard deviations are exact for the printed populations (obviously for sub populations of these may vary). The full details of the distributions is on the enclosed lesson ideas sheet. If you want to get fancy, pause the print a few layers before the end and change the filament color. This makes the numbers easier to read and makes the levels on the histogram clearer.

The prints are relatively big, but they are simple. No support is needed and there is plenty of contact with the bed so nothing should move around. I printed mine with a 0.4mm nozzle and 0.3mm layer height. They all fit on my 120mm x 120mm bed.

If you want a bigger or smaller tray use the customizer tied to this thing. The customerizer also have an option to leave the numbers off the tray. This allows you to print several trays and hook them together to cover wide ranges of numbers. The OpenScad file for peg sets is also included if you want to make your own populations. I tried to make it available via the customerizer, but it appears the customizer doesn't do random numbers correctly, so you'll have to run it on your own in OpenScad. There is also a set of blank pegs if you just want to write numbers on the pegs.

(Please excuse the ridges on everything, I discovered after printing this my base wasn't secured well and was wobbling a bit during the print)

• 3D file format: STL