Experimental Design B/C

[Liv]

Hi.I'm doing Experimental, but i sorta need help.

Can anyone give examples of IV and Qualitative Observations? Like what you would write for an event.

IVs(Independent Variables) are the factors that can be varied or manipulated in an experiment. Like for example, say you are doing an experiment on how the mass of a ball effects it's bounce height, the independent variable would be the different masses of the balls, because it is being PURPOSELY changed in the experiment.

Qualitative Observations are observations that you observe with your five senses, touch, smell, sight, taste and hearing. For example, a Qualitative observation for the experiment stated above would be, in the middle of the experiment, when the ball hit the ground it bounced out of the testing area.

[nejanimb]

Hey guys, what would you do for Example 8 on the Experimental Design Practice Wiki? Me and my partner are stumped.

I can come up with a few...creative...experiments, but the most straightforward one seems to be to change up the type of writing utensil used since they give you three of them. ANd do what with them? You could hold them perpendicular to a sheet of paper and draw a line. Measure the thickness, rinse and repeat. Your dependent variable, then, is thickness of the writing utensil. You could also make a dot with each writing instrument and measure its diameter. Then compare the diameters of dots made by each writing instrument.

I suppose you could also roll each across the table and see how far they go, you know, if they differ. This would be a pretty poor experiment, though...

Uncapped marker, vary the drop height and record the area of the dot it makes when it hits the paper below it, I think I would do.

Annoying set of materials, but definitely forces some creativity.

[GoNerdHerd]

What have you guys been getting for materials at competitions?

[amerikestrel]

What's the difference between sample and population standard deviation?

[Skink]

What's the difference between sample and population standard deviation?

Sample standard deviation is the one you calculate in your experiment, from your "sample". The one of a population is the "actual" one. Here's an example that might help...

My experiment gives me 5 people (okay, not in this event, but for this example...) and the topic of intelligence. I administer IQ tests to all 5, score them, and calculate the standard deviation. That's my sample standard deviation, coming from my sample of 5 participants. I can do statistics and garbage to compare it to the population standard deviation which happens to be 15, if I recall correctly. That make sense, a little? Why do you need population standard deviations in this event?

[nejanimb]

Sort of - it doesn't mean that the standard deviation of your sample is difference, it means you have to use a different method of calculation if you're using your sample data to make a conclusion about the population. It has to do with the way you calculate it. 1/n vs. 1/(n-1).

Basic statistical explanation: the point of drawing a sample is to estimate something about the population. You pick an estimator for a parameter. When you do a scientific experiment, you're trying to make a generalization about the "true" value that governs the relationship of concern. The true standard deviation is a population parameter, and so you pick an estimator to make a statement about that. An estimator can be anything whatsover - it can be a total guess, it can be a median, it can be a strange, incomprehensible function, so long as it's a function of the sample data you collected (again, even if that function is "arbitrary guess"). One important thing about what estimator to choose is that you want it to be unbiased - that is, the expected value of the estimator is equal to the value of the population parameter. sqrt((sigma(x-xbar)^2)/(n-1)) is an unbiased estimator for the population standard deviation. sqrt((sigma(x-xbar)^2)/n) is an asymptotically unbiased estimator - that is, as n approaches infinity, this becomes an unbiased estimator (and is an estimator you might come up with using a moment generating method of finding them). Therefore, you use that when you are considering the entire population. With large n, it doesn't make a big difference, but with the quantities you're using in Experimental Design (usually 3, so n-1 is just 2), it makes a big difference.

Very simplified. Hope it helps.

[sciolyscorpio95]

Hi.I'm doing Experimental, but i sorta need help.

Can anyone give examples of IV and Qualitative Observations? Like what you would write for an event.

IVs(Independent Variables) are the factors that can be varied or manipulated in an experiment. Like for example, say you are doing an experiment on how the mass of a ball effects it's bounce height, the independent variable would be the different masses of the balls, because it is being PURPOSELY changed in the experiment.

Qualitative Observations are observations that you observe with your five senses, touch, smell, sight, taste and hearing. For example, a Qualitative observation for the experiment stated above would be, in the middle of the experiment, when the ball hit the ground it bounced out of the testing area.

This is what my team thought the definitions were, but so far at 3 invitationals and States last year, the proctors have been saying that we have the variables wrong, and that the DV is what you change or manipulate and the IV is what you observe. This has been really annoying my team because that was a factor that cost us Nationals last year (we got 3rd by one point).

[Skink]

Hi.I'm doing Experimental, but i sorta need help.

Can anyone give examples of IV and Qualitative Observations? Like what you would write for an event.

IVs(Independent Variables) are the factors that can be varied or manipulated in an experiment. Like for example, say you are doing an experiment on how the mass of a ball effects it's bounce height, the independent variable would be the different masses of the balls, because it is being PURPOSELY changed in the experiment.

Qualitative Observations are observations that you observe with your five senses, touch, smell, sight, taste and hearing. For example, a Qualitative observation for the experiment stated above would be, in the middle of the experiment, when the ball hit the ground it bounced out of the testing area.

This is what my team thought the definitions were, but so far at 3 invitationals and States last year, the proctors have been saying that we have the variables wrong, and that the DV is what you change or manipulate and the IV is what you observe. This has been really annoying my team because that was a factor that cost us Nationals last year (we got 3rd by one point).

I find that...really, really hard to believe. No adults in a competition called SCIENCE Olympiad would make an error as egregious as that.

[sciolygrl258]

Well, believe it or not, its true.
Once the protors stapled a sheet with all the definitions onto the test, and it had the wrong definitions on it. We didnt follow the sheet that they gave us b/c we knew that it was incorrect, and got all of it wrong...

[AlphaTauri]

That is seriously messed up...there's a reason DV stands for Dependent Variable because guess what? It DEPENDS on the independent variable.

Edit: sciolyscorpio, this was at PA States? Wow...I expect better from such a generally well-run state.