Tag Archives: experiment design

hdwkt: the science behind nutritional advice

9 Nov

The past few years I’ve been teaching biochemistry of the macromolecules (Chapter 3 in Campbell Concepts and Connections) alongside enzymes and digestion (Chapters 5 and 21 respectively). To me, these topics fit together tighter than a-bungarotoxin at the neuromuscular junction. I wish more textbooks would organize themselves this way, rather than oh so unoriginal small – big sequence of topics. Start with atoms, end with ecology…clever. But that’s another day.

A few items recently caught my eye regarding nutritional advice, and I’m mulling over how to implement these into the classroom along the lines of hdwkt (how do we know this?). One is a video a student showed me of  a 4 year old McDonald’s hamburger that looks pretty much like a 4 hr old hamburger (there’s lots of other videos on this same theme).

While her props are indeed provocative, this isn’t really fair to the burger or fries. Before I start, I’m not in any way suggesting that McDonald’s is healthy or great for you, or that any burger and fries are great for you. However, I do take issue with her illogical argument for avoiding McDonald’s.

Her argument goes something like this:

McDonald’s burger doesn’t rot
Food rots
Therefore, McDonald’s burger is not food

Her corollary to that seems to be:

McDonald’s non-food burger doesn’t break down easily in the open air under normal household conditions
If non-food burger can’t break down outside the body, it can’t break down inside the body
If the burger can’t break down, your body stores it (in your thighs)

There’s lots of ways this line of reasoning is flawed. Skipping over the philosophical debate over a definition of ‘food’, even a rudimentary working knowledge of the digestive system would tell you that the environment in your stomach or small intestine is quite different from sitting on the kitchen counter. I think this provides a great opportunity for students to critically evaluate an argument such as this and apply knowledge they’ve acquired.

Another issue here is the lack of a proper experiment. Simply holding up one McDonald’s burger doesn’t tell us much when we don’t have another burger to compare it to. Similarly, slices of raw potato don’t make a great control for a McDonald’s french fry longevity study aimed at demonstrating how un-foodlike McDonald’s products are. What would make a better control? What types of experiments could we design?

Today I stumbled across a blog post from J.Kenji-Lopez (SeriousEats.com) who seems to have taken issue with this pseudoscience of burger preservation and tried to approach it more scientifically. Read more about the experiments and analysis here. I like the comparison of % change in mass over time graph, interesting stuff.

This provocative video lecture, “Sugar: The Bitter Truth” by a scientist from UCSF argues that fructose is treated by our bodies as a poison and responsible for the modern obesity epidemic. Lots of great biochemistry too. This isn’t exactly a mainstream, FDA position, but that’s the point. How do we evaluate these types of claims? It gets even harder when it’s a scientist from a reputable university, and he’s using lots of formulas! How does the FDA make their guidelines? When you take a look at the obesity epidemic, obviously something about or recommendations isn’t working…

Another food related article illustrates the uncertainty in our scientific understanding of world. The headline ‘Twinkie diet helps nutrition professor lose 27 pounds” is definitely an attention grabber. There’s lots of room for questioning in here. Why do we eat the foods we do? A great food choice related infographic appeared in the NYTimes the other week highlighting ways we can subtly alter school cafeterias to increase positive choices. Reminded me of the book ‘Nudge’ a bit, but how do we know what is ‘good’?

Everyone is faced with food choices every day of their life. How can we better inform our choices? My students will soon be heading off to college and, for many of them, it will be the first time in their lives when they’re entirely responsible for what to eat. Yikes.

Michael Pollan has written extensively on food and nutrition and I really enjoy his perspective. His book, “In Defense of Food,” has a nice and simple message, “Eat food, mostly plants, not too much.” Word.


Doing labs the Write way

29 Jul

I like things that make my life easy. I like things that make my students’ lives easy. Things that do both? Pure awesomeness. And so it is with LabWrite.

You can't go wrong with LabWrite

I spent my first couple of years as a teacher “experimenting” with various styles of lab reports and lab notebooks. Sometimes grading makes me grumpy. Often times, the quality of these reports sucked was less than satisfactory. This made me grumpier. Then it was time to grade more labs. It was a vicious cycle of grumpiness.

I have only myself to blame. If you haven’t entirely bought into the set of “rules” for reporting on labs that you’re giving to your kids, your students sure as hell won’t. Annual tweaks to the guidelines or rubric helped a bit, but at some point you can’t polish a turd. Switching to LabWrite last year made my life easier, helped students understand the process of science better, and helped me lose 30 lbs in 30 days! (Ok, I made that last part up)

Here’s why I’m digging LabWrite:

  • Intuitively organized into sections – PreLabInLabPostLab
  • Each item is defined and clearly explained
  • Detailed, but still flexible for different types of labs e.g. inquiry-based, hypothesis w/ predetermined procedure, demonstration labs, etc
  • The interactive tutor guides the writing process for each section of the report with questions to probe student thinking
  • Most importantly, students enjoy using it (eventually) and the quality of labs compared to previous years is WAY better.

I’ll quit talking it up (until NC State starts showin me the $) and let you check it out on your own.

Anyone used this for Chemistry or Physics classes? I’m interested to hear your feedback. I picked up a section of Chemistry for this coming fall and would like to use it for Chem labs as well…thoughts?

is this data significant?

26 Jul

If the word kurtosis brings to mind Grandma and a desperate need for Listerene, then we’re probably in the same boat when it comes to statistics. I love numbers, data, infographics, etc, but statistical tests have always challenged my patience intellect. For the longest time, I felt p values were like those magic eye paintings where you stare at them for awhile in frustration, and then when you finally glimpse a bit of what might be the image (is that a triceratops? sailboat?), you blink and the image vanishes.

magic eye image

magically annoying

Needless to say, this summer I bit the bullet and took a class in experimental design, methods, and stats as part of my masters degree. Totally changed my understanding of how statistics fit into science. I’ve still got plenty to learn, but I’ve resolved to take my newfound appreciation for statistical analysis and revamp my lab curriculum.

I mentioned in a previous post my recent change to teaching evolution first. One of the first lab activities I usually do is something to demonstrate the variation that exists in populations (e.g. measuring height/weight data in class, etc.).

I’ve taken this idea and created a scenario-based lab where students have to figure out a way to compare two populations. Here’s a snippet:

“Just the other day your boss, Pedro, was thanking you for saving the store money after you found a new local mealworm distributor offering cheaper prices. A few dead reptiles later, and your boss is threatening to fire you. He claims the new mealworms you ordered are different, and he’s blaming the new worms for his dead reptiles. And you thought all mealworms were created equal.

You need to design an experiment or experiments to determine if there is a significant difference in the two populations.

How will you ensure standardized data collection procedures? What outside factors might influence your data collection? How will you use the data you collect to make a comparison? How can you quantify the differences between the two populations (or lack thereof)?”

This of course leads into all sorts of interesting discussions related to statistics. This could be a little statistical appetizer or a whole can of worms, depending on the direction you want to go. By my count, at least three different statistical tests could be used to compare the samples, one of which barely requires any calculations (tukey’s quick test).

Like what you see? Download the whole shebang here: MealWormStats

(CORRECTION: Mann-Whitney U test actually compares the median values of two populations, not the mean and has been corrected in the file posted above.)

Feedback welcome.

how much is inside ______?

24 Jul

Measurement is a fundamental skill in science, and the question of “how much inside” is an often practical question. The answer may be intriguing and occasionally humorous (see below). For students, this basic question presents some different lines for problem solving and inquiry. How to go about measuring it? What data to collect? How to present the data? Do two populations differ in how much is inside?

Here’s an example: How much is inside a samosa?

Samosas are delectable triangles of deep-fried goodness. But what is it exactly that contributes to their irresistibility? In an attempt to better understand the delicious mysteries of the samosa, we carefully examined this culinary treat’s inner workings.

Continue reading

in the beginning there was……science

22 Jul

My love affair with science goes back as far as I can remember, and it has relentlessly influenced my life since. It’s also the lens through which I view pretty much everything, this blog included. Now that I’ve gotten that off my chest, let the fun begin.

Speaking of beginnings, I’ve been thinking a lot about the start of this school year.  It’s no revelation that minute one, day one sets the stage for the rest of the year. I’ve always been a big believer in hitting the ground running, but this year I’m looking to take it up a notch. Here’s my day-to-day plan for this year:

  1. Provocative image/video showing on screen when students are walking in
  2. 1-2 questions as a lead in to the topic of the day/week/etc
  3. Take out writing instrument. Start writing. There is no wrong answer.

While a Mylie Cyrus photo tweet may qualify as provocative, not exactly what I’m going for here.

Here’s a preview of day one in AP Bio this year, opening the ecology unit:

I want to set the tone right from the start that it all starts with unexplained observations and the quest to find an explanation. How would we go about figuring out what’s going on here? What kind of experiments could we design to test our initial ideas? This is where I want to go all year long

Another sneak peak….Bio class day one, evolution and a video (sans audio) of a Devil’s garden (irony?):

We’re going down the evolution road, but first, what’s happening here? Next, how did we get here? No solutions yet – just discussion – we’re just whetting the appetite a bit. We’ve got plenty of Darwinian ground to cover first, but I we’ll get to that soon enough…

Note: Last year I decided to take the traditional micro to macro course sequence and turn it on its head. Why save the best for last? Let’s put evolution where it belongs, as the foundation that biology is built on.  Couldn’t be happier with the choice and looking forward to building (sorry…) on last year’s changes.