Experimental Design B/C

[Crazy Puny Man]

We were given a toy car, a paper towel roll, and a block. So we made a ramp with the paper towel roll and block, and then measured how far the car rolled. We related it to the coefficient of friction, where friction was rubbing against the wheels making it slow down and ultimately go less distance

No I'm not.

So you calculated the coefficient of friction as your dependent variable and the distance the car rolled as the independent variable?

How would you calculate the coefficient of friction though? You don't know the mass or any of the other information needed to calculate it.

I think their dependent variable was the distance it rolled, they just included the coefficient of friction to impress their judges (yes?). I mean, the coefficient of friction would stay the same as long as the surface you use throughout the experiment is the same...

And if mass is your independent variable, I do not believe that the distance should change. In all cases, whenever you roll the object down the ramp, your acceleration is g, 9.8 m/s2 (for those of you who brought up F = ma, in this case, a = g, so your force gravity = m x g). While the force gravity would increase, acceleration does not, since g does not change.

[Phys1cs]

We were given a toy car, a paper towel roll, and a block. So we made a ramp with the paper towel roll and block, and then measured how far the car rolled. We related it to the coefficient of friction, where friction was rubbing against the wheels making it slow down and ultimately go less distance

No I'm not.

So you calculated the coefficient of friction as your dependent variable and the distance the car rolled as the independent variable?

How would you calculate the coefficient of friction though? You don't know the mass or any of the other information needed to calculate it.

I think their dependent variable was the distance it rolled, they just included the coefficient of friction to impress their judges (yes?). I mean, the coefficient of friction would stay the same as long as the surface you use throughout the experiment is the same...

And if mass is your independent variable, I do not believe that the distance should change. In all cases, whenever you roll the object down the ramp, your acceleration is g, 9.8 m/s2 (for those of you who brought up F = ma, in this case, a = g, so your force gravity = m x g). While the force gravity would increase, acceleration does not, since g does not change.

the topic was friction. So because we were changing the surface the car was rolling down (paper towel, table, sandpaper), we related the distance of the car rolled (dependent) to the surface (independent). Control was the table (it was one of those acid/fireproof tables in labs) We then said that the friction of the cars wheels with the surface was causing change in how far the car rolled. We used coefficient of friction just as a mathematical way of backing up what we were saying.

[Crazy Puny Man]

I know, I was just clearing up any misconceptions that might've existed...I wasn't exactly sure of what people were and weren't getting

Hm, and Asteroidea makes a good point. How would you quantify your IV? How did you plot it on the x-axis of your graph?

[phil9047]

the topic was friction. So because we were changing the surface the car was rolling down (paper towel, table, sandpaper), we related the distance of the car rolled (dependent) to the surface (independent). Control was the table (it was one of those acid/fireproof tables in labs) We then said that the friction of the cars wheels with the surface was causing change in how far the car rolled. We used coefficient of friction just as a mathematical way of backing up what we were saying.

Are you sure that the control was the table? Isn't control a group of IV in your experiment?

Also, is it necessary to quantify your IV? It doesn't explicitly state that in the rubric.

[Crazy Puny Man]

the topic was friction. So because we were changing the surface the car was rolling down (paper towel, table, sandpaper), we related the distance of the car rolled (dependent) to the surface (independent). Control was the table (it was one of those acid/fireproof tables in labs) We then said that the friction of the cars wheels with the surface was causing change in how far the car rolled. We used coefficient of friction just as a mathematical way of backing up what we were saying.

Are you sure that the control was the table? Isn't control a group of IV in your experiment?

Also, is it necessary to quantify your IV? It doesn't explicitly state that in the rubric.

The table is one of the levels of the IV in his experiment, based on his description

If you don't quantify your IV somehow, then going to plot your data is going to be kind of awkward. Your x-axis will be qualitative, not quantitative, and you won't be able to perform linear regressions, etc.

[phil9047]

Wait, so is it recommended that the graph be a plot chart? In the case that the IV is not quantified, can't I just use a bar graph and say the line of best fit is inapplicable in our experiment? Or should I just stick with the rule that I should quantify my IV?

[Voltage]

Wait, so is it recommended that the graph be a plot chart? In the case that the IV is not quantified, can't I just use a bar graph and say the line of best fit is inapplicable in our experiment? Or should I just stick with the rule that I should quantify my IV?

Here's what my team generally does:

If the IV consists of numbers, for example, dropping something from 10 cm, 20 cm, and 30 cm, we generally use a dot plot and draw a line of best fit if it is applicable.

If the IV consists of materials, for example, dropping paper, folded paper, and crumpled paper, we generally use a bar graph and do not draw a line of best fit even if there appears to be one.

Being from Div. B, the latter choice is okay since we don't have to do regression analysis or any of that other stuff. I can see that you are from Div. B as well, so you can probably do a similar thing.

For someone from Div. C, however, my guess is that you have to quantify your IV.

Note that line of best fit is part of Statistics, and that it is an "or" thing. You could just do Average and Range and cut it off there.

[Phys1cs]

the topic was friction. So because we were changing the surface the car was rolling down (paper towel, table, sandpaper), we related the distance of the car rolled (dependent) to the surface (independent). Control was the table (it was one of those acid/fireproof tables in labs) We then said that the friction of the cars wheels with the surface was causing change in how far the car rolled. We used coefficient of friction just as a mathematical way of backing up what we were saying.

Are you sure that the control was the table? Isn't control a group of IV in your experiment?

Also, is it necessary to quantify your IV? It doesn't explicitly state that in the rubric.

The table is one of the levels of the IV in his experiment, based on his description

If you don't quantify your IV somehow, then going to plot your data is going to be kind of awkward. Your x-axis will be qualitative, not quantitative, and you won't be able to perform linear regressions, etc.

]

Yes, our IVs were the table, the sand paper, the paper towel, and the felt that we were given. The table just also served as the control.

Yes, we used a bar graph. We plotted the average run distance on each of the surfaces. For divC at least, we did then the mean, median, mode, range, standard deviation, and variance. Line of best fit is one of those "or" things. When we do that, we always include their r values.

as for what phil9047 said, usually trying to get the IV to be able to be something that works well with a line graph. It just makes the write up and statistics easier, as you can say slope means.. and such. If not, like our car lab, then you just have to go about interpreting your data in a different way.

Posthumously, I just realized we could have timed how long until the car stops. That would have included a time factor, which is an easy way to make it line-graph able. It still related to friction and you can incorporate the coefficient of friction the same, but would have given you "better" stats to look at.

[Asteroidea]

Hmm I never thought to use a bar graph, I guess it's been drilled into our head so much that your graph MUST be a dot plot of some sort...I also seem to recall someone (a moderator perhaps?) saying that both your variables should always be quantifiable...

[Phys1cs]

Hmm I never thought to use a bar graph, I guess it's been drilled into our head so much that your graph MUST be a dot plot of some sort...I also seem to recall someone (a moderator perhaps?) saying that both your variables should always be quantifiable...

dot plots are much easier and give you much better statistics and ways of analyzing your data. Though with a bar graph, you can kind of get the same thing. You will notice (sometimes) one is much smaller, or it goes down linearly (like in our car/friction lab). There are still trends you can find within the data, it just sometimes may be harder, or you have to be more convincing with the statistics you do have, because you wont have that slope, or curve.