Archive for category Education
Magic of multifactor testing revealed by fun physics experiment: Part One—the setup
Posted by mark in design of experiments, Education on August 23, 2020
The behavior of elastic spheres caught my attention due to a proposed, but not completed, experiment on ball bounciness turned in by a student from the South Dakota School of Mines and Technology.* I decided to see for myself what would happen.
To start, I went shopping for suitable elastic spheres. As pictured, I found two ball-toys with the same diameter—one of them with an eye-catching Spider-Man graphic.
My grandkids all thought that “Spidey” would bounce higher than the other ball—the one in swirly blue and yellow. Little did they know just by looking that “Swirley” was the one with superpowers, it being made from exceptionally elastic, solid synthetic rubber. Sadly, Spidey turned out to be a hollow airhead. This became immediately obvious when I dropped the two balls side by side from shoulder height. Spidey rebounded only to my knee while Swirley shot all the way back to nearly to the original drop level, which really amazed the children.
My next idea for the bouncy experiment came from Frugal Fun for Boys and Girls, a website that provides many great science projects. Their bouncy ball experiment focuses on the effect of temperature as seen here.
However, I could see one big problem straight away: How can you get an accurate measure of bounce height? That led me an amazing cell-phone app called Phyphox (Physics Phone Experiments) which provided an ingenious way to calculate how high a ball bounces by listening to them hit the floor.** Watch this short video to see how. (If you are a physicist, stay on for how the narrator of the demo, Sebastian Staacks, worked out all his calculations for the Phyphox (In)elastic tool.)
The third factor came easy: Height of drop. To make this obvious but manageable, I chose three versus six feet.
The fourth and final factor occurred to me while washing dishes. We recently purchased a thick rubber mat for easy cleanup and comfortable standing in front of our sink. I realized that this would provide a good contrast to our hardwood floors for bounce height, the softer surface being obviously inferior.
To recap, the four factors and their levels I tested were:
A. Ball type: Hollow or Solid
B. Temperature: Room vs Freezer
C. Drop height: 3 vs 6 feet
D. Floor surface: Hardwood vs Rubber
Using Design-Expert® software (DX) I then laid out a two-level, full factorial of 16 runs in random order. To be sure of temperature being stabilized, I did only one run per day, recording the time the first bounce and its height (calculated by the Phypox boffins as detailed in the videos).
When I completed the experiment and analyzed the results using DX, I was astounded to see that neither the type of ball nor the differing surfaces produced significant main effects. That made no sense based on my initial demonstrations on side-by-side bounce for the two balls on the floor versus the rubber mat.
Keeping in mind that my experiment provided a multifactor test of two other variables, perhaps you can guess what happened. I will give you a hint: Factors often interact to produce surprising results, such as time and temperature suddenly coming together to create a fire (or as I would say as a chemical engineer—an “exothermic reaction”).
Stay tuned for Part 2 of this blog on my elastic spheroid experiment to see how the factors interacted in delightful ways that, once laid out, make perfect sense to even for non-physicists.
*For background on my class and an impressive list of home experiments, see “DOE It Yourself” hits the spot for distance-learning projects.
**I credit Rhett Alain of Wired for alerting me to Phyphox via his 8/16/18 post on Three Science Experiments You Can Do With Your Phone. From there he provides a link to a prior, more detailed, post on Modeling a Bouncing Ball.
“DOE It Yourself” hits the spot for distance-learning projects
Every spring for the last two decades I travel to Rapid City to teach design of experiments (DOE) for the Department of Chemical and Biological Engineering at the South Dakota School of Mines and Technology (SDSMT). The highlight of these classes comes when students compete in a flyoff of their paper helicopters developed via the multifactor tools of DOE. They provide an awesome demonstration of design of experiments.
Unfortunately, the Covid-19 pandemic made it impossible for students to team up this year. However, this provided the opportunity for them to each do their their own experiments. I provided an extensive number of suggestions via this DOE It Yourself compilation. Most of the students chose one of these, but a few came up with new ones, such as the one of legal drinking age who sipped tiny amounts (for tasting only, I was assured) of variously concocted Margaritas. The variety of experiments amazed me:
- Cooking eggs to perfection
- Playing tabletop hockey
- Blending a most refreshing Margarita
- Shooting Nerf arrows
- Sharpening up hand-eye coordination
- Flying paper helicopters
- Soaking colors into celery
- Finding fabrics with maximum absorbency
- Making the perfect cup of coffee
- Baking delicious cookies (I asked to be on the taste panel for round 2)
- Mixing good Gatorades
- Producing the perfect puffed rice
- Manufacturing fearsome fighter jets
- Catapulting projectiles with a clothes-pin
- Chipping golf balls more accurately (I wish this could translate to my game)
- Breaking paper clips for stress relief
- Creating craters in the kitchen
- Spinning balls down a funnel
- Sinking boats with too much treasure (see video by Nghia Thai )
Congratulations to SDSMT and their students of DOE for such great work—them not letting the pandemic get in the way for learning how to experiment more effectively via these statistically rigorous, multifactor methods.
Over half of all children have below-average reading skills
Posted by mark in Education, leadership, pop, Uncategorized on June 24, 2019
Yes, you read that right—this statistic was cited by Eugenia Cheng last weekend in her column for the Wall Street Journal on why Averages Aren’t Always What They Seem. In this case, a small number of excellent readers skews the distribution to the right.
But none of this applies to my offspring, them being in the Lake Wobegon region where all the children are above average.
I would never admit it, but deep down I realize that I’ve succumbed to the superiority illusion, aka the Dunning-Kruger effect. As advised in this June 3rd post by Forbes you’d best be careful not to be taken in by individuals who consistently overestimate their competence due to this cognitive bias.
Steve Carell took the superiority illusion to an absurd extreme as the manager Michael Scott in the “The Office” television series. It’s funny unless you are subject to someone like this.
“The knowledge and intelligence that are required to be good at a task are often the same qualities needed to recognize that one is not good at that task—and if one lacks such knowledge and intelligence, one remains ignorant that one is not good at that task.”
— David Dunning, professor of psychology at the University of Michigan
“Stupid people are so stupid they’re unable to grasp the fact that they’re stupid.”
— Letter to Editor of Oroville Mercury Register, 6/23/19
Dream come true: Homework banned and school days delayed
The Wall Street Journal this week reports that, for the sake of “student wellness”, school districts across the USA are now banning homework [1].
The U.S. Department of Education figures that, on average, high-school students (those without the “get of jail free” card) spend about 8 hours per week on extracurricular assignments. Girls spend an hour more than the norm and boys an hour less, thus there’s a two-hour gender gap on homework. (You be the judge as to what this implies on relative intelligence. I don’t dare!)
Naturally, parents with ambitions for their son or daughter do not favor this trend to relieve academic pressure. Many evidently move their child to private schools that load on several more hours of homework every week. That would be a blow—being yanked away from all your friends at Easy Street High.
It would be worth it if more homework leads to a significantly better education. WSJ suggests that this may not be so for elementary students. That seems sensible. But what about high school? The author of The Battle Over Homework, Duke professor Harris Cooper, says that studies show a positive correlation of homework with achievement [2]. He advises that high-schoolers put in at least 90 minutes a night but beyond 2.5 hours the returns diminish (and any chance of a social life).
Meantime, other school districts, perhaps some that ban homework (that would be double dope!), have moved back their start times to provide more sleep for students. For the heads up, see these Shots from the December 12th NPR Health News on Sleepless No More In Seattle.
I can only say that my quarter of 8 am organic chemistry as a freshman at university did not go well. My notes provided a record of frequent nodding off by my pen trailing off every few lines. That was before I discovered coffee and became addicted to rising early.
Weakest students hurt worst by shift away from face-to-face teaching
The January 21 New York Times featured a thought-provoking critique* of online courses by Susan Dynarski, a professor of education at the University of Michigan. She cited growing evidence that the trend away from classroom training in high schools and colleges hurts less proficient students who need ‘hand-holding’ from skilled teachers. However, research suggests that the greatest harm comes from courses going fully online. “Blended” training, which presents the opportunity for interaction with a flesh-and-blood teacher, evidently overcomes this disadvantage.
An interesting wrinkle on blending face-to-face with online education comes from the Massachusetts Institute of Technology. They offer free online courses on economics. Students who do well can apply for a master’s program which requires only one semester of class on MIT’s Cambridge campus to graduate. This weeds out those with weak academic skills, whereas many high schools mistakenly go the opposite route—students failing face-to-face classes get sent to remedial online classes.
“For advanced learners, online classes are a terrific option, but academically challenged students need a classroom with a teacher’s support.”
-Susan Dynarski
*”Online Courses Fail Those Who Need Help”, p3, Sunday Business Section.