Experimental Design B/C

[quizbowl]

There's a rubric on the soinc.org page of Experimental Design - it would be wise to look that over.

[wertyu793]

JCCC in KS did not have a topic to work on for regionals. When we got to state last year, thery gave us a certain task and we were under prepared. This year we are much better.

[zyzzyva980]

As I recall, at regionals they gave us several household substances like baking soda, vinegar, etc. At state, they didn't give a certain *task*, just a topic- energy conservation if I remember correctly. A simple ramp would work. Don't overthink it- I saw one team try to use "solar power" from a nearby window.

[49ers]

what exactly would be the corerct order in which to write up a lab?

[Phenylethylamine]

As I recall, at regionals they gave us several household substances like baking soda, vinegar, etc. At state, they didn't give a certain *task*, just a topic- energy conservation if I remember correctly. A simple ramp would work. Don't overthink it- I saw one team try to use "solar power" from a nearby window.

The rules aren't very specific on this point, but it does say that they should give you a topic of sorts. There's no information on how narrow this topic can or should be, so it varies a lot. Sometimes you just get a general topic, like energy conservation; others they give you a certain task. In my experience, it's more common to get a very open-ended topic than a clear task.

[tclme elmo]

Every single test I've taken this year has been either Design an experiment related to force and motion, or literally, a given problem statement about force/motion. The easiest experiment is to just to gravitational force, as you already know the answer. All the tests I've done this year are pretty much the same, just different materials and procedure. But when you can, I'd suggest doing something like that.

[eeldj123]

Just curious, but would someone be able to explain these parts of the rubric?

- Observations about results not directly relating to Dependant Variable
- Measure of central tendency
- Suggestion for other ways to look at hypothesis given
- Standard of Comparison


Thanks in advance.

[nejanimb]

1. Pretty much exactly what it says. Do a list of qualitative observations, and make sure some of them don't have to do with the dependent variable, ie: "The floor is slick and smooth," or "the ball has a strong lavender smell."

2. Mean. Could be median, but almost always the mean. Usually calculated separately for each level of IV.

3. The trickiest point on the rubric, in my opinion. From my post on the subject a few pages ago:

"That one was always the fuzziest. A natural interpretation would be "given this hypothesis, what's one other way we could test it?" Another option is "analyze your hypothesis critically and come up with some other things it might imply, and look for "other things it might say." I wish I could give a better answer for this one - it's weird!"

4. Standard of comparison should be a trial value that you can compare everything to. Sometimes it'll mean repeating a the first level at the beginning and at the end of the experimentation so that you can see if the materials have changed during the course of an experiment; that is a common way to handle it. Another is to choose a level that is a "baseline" - for instance, if you have a ramp experiment but the table surface you'er using is a bit slanted, you can use a "ramp incline of 0" to show that even without any increments to the level of the ramp, the ball or whatever still moves, so you can compare everything else to that baseline level. For SoC, state what your standard of comparison is, why that is a viable choice for a standard of comparison, and then explain the values you actually got and how things appear to compare.

[eeldj123]

1. Pretty much exactly what it says. Do a list of qualitative observations, and make sure some of them don't have to do with the dependent variable, ie: "The floor is slick and smooth," or "the ball has a strong lavender smell."

2. Mean. Could be median, but almost always the mean. Usually calculated separately for each level of IV.

3. The trickiest point on the rubric, in my opinion. From my post on the subject a few pages ago:

"That one was always the fuzziest. A natural interpretation would be "given this hypothesis, what's one other way we could test it?" Another option is "analyze your hypothesis critically and come up with some other things it might imply, and look for "other things it might say." I wish I could give a better answer for this one - it's weird!"

4. Standard of comparison should be a trial value that you can compare everything to. Sometimes it'll mean repeating a the first level at the beginning and at the end of the experimentation so that you can see if the materials have changed during the course of an experiment; that is a common way to handle it. Another is to choose a level that is a "baseline" - for instance, if you have a ramp experiment but the table surface you'er using is a bit slanted, you can use a "ramp incline of 0" to show that even without any increments to the level of the ramp, the ball or whatever still moves, so you can compare everything else to that baseline level. For SoC, state what your standard of comparison is, why that is a viable choice for a standard of comparison, and then explain the values you actually got and how things appear to compare.

Thanks so much for explaining!
Can I ask if my suggestion for other ways to look at a given hypothesis and SOC (in an upcoming example) would be valid?
Let's say I was doing a temperature lab that includes looking in which my team looks at how temperature changes in a solution with hot water and different substances (ex. MG, Salt, Toothpaste, etc. Like Example 3 in the wiki).

Thanks again for the explanation. (:

If my hypothesis is that the solution of hot water and MSG will have the greatest drop in temperature, would another way to look at it be hypothesizing that rather than the solution of hot water and MSG that the solution of hot water and toothpaste will have the greatest drop in temperature during a given interval of time?

As for the SOC in this case, would it be like comparing the results to a solution of only hot water? If so, then would the SOC be similar the controlled trial (in this case, a solution of only hot water to show that the temperature will drop on its own)?

[nejanimb]

First, that would definitely be the wrong choice of experiment to do given that set of materials and instructions. It's hard to say whether your "another way of looking at the hypothesis" would be a valid choice, since your choice of hypothesis isn't really valid. But, in any case, simply hypothesizing a different result is not the way to do it.

Instead, let's say your problem statement was "How does the concentration of NaCl in a solution affect the rate of heat loss of the solution?" and you measured this by creating different samples of the solution and heating the solutions and measuring the change in temperature of each after 60 seconds (probably not the experiment I would have chosen, but that's at least a valid option and was fairly close to your suggestion). You hypothesize that the concentration and rate of heat loss are indirectly linearly related, with your explanation being that there being more material dissolved in the water causes the molecules to be more tightly packed and retain heat better (this is entirely made up).

Your "alternative way to look at the hypothesis" could then be that "The density of an aqueous solution and its rate of heat loss are indirectly and linearly related," and you explain that this is another way of looking at the same thing because the rationale for your original hypothesis was actually based on the density, so this version of the hypothesis essentially asks the same question.

Your suggestion for SOC was perfect though. Definitely in this case you would use "concentration = 0" and measure heat loss, and you would also test it at the beginning and end of your experimentation and explain that that part helps you check for changes in ambient conditions.

Hope that helps!