Experimental Design B/C

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Experimental Design B/C

Postby Jim_R » August 10th, 2014, 10:49 am

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Re: Experimental Design B/C

Postby HeavyHitter406 » September 25th, 2014, 3:44 pm

I'm new to division C...how do you do Standard of Deviation? That is part of the Statistics in C, right?
2014 (Wright State/Lisle/Grayslake/Regionals/State/Nationals)

Water Quality: 8/1/2/1/2/3
Experimental Design: 12/1/5/5/8/37
Road Scholar: 12/2/2/3/3/11
Wheeled Vehicle: 32/6/6/2/11/5

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Re: Experimental Design B/C

Postby actionpotential » September 25th, 2014, 5:19 pm

Hey Heavyhitter!

So I've always been confused by that big complicated expression myself. Standard deviation is basically measure of how spread out your data values are.

Analyzed step by step:

1. Take the mean of the data. (Symbol is x with bar over it)
2. For each data point, subtract mean from the data point. Then square this difference.
3. Add up the squares.
4. Divide this sum by number of terms minus 1. (Symbol of number of terms is n.)
5. Take square root.

For example:

Data set: 1, 3, 5, 7, 9

1. Mean = 5
2 and 3. (1 minus 5)^2 + (3 minus 5)^2 + ... = 40
4. 40 divided by (5 minus 1) = 8
5. Square root of 8 = 2.828

Standard Deviation = 2.828


Note:If your data includes possible data points for a population, then in step 4 you would instead divide by the number of terms. But if you're working with a sample of the data, which is probably the case in XPD, you divide by number of terms minus 1.

Ex. If you're analyzing the height of ALL students in your grade level, then you divide by number of data values. If you analyze the height of a randomly selected, representative sample of students in your grade level, you divide by number of data values minus 1.

Alternatively, since you can calculate Standard Deviation on your Scientific/Graphing calculator. Plug data in Stat, and use 1-var stats. Standard deviation is round-greek symbol with line out.



Good luck :D

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Re: Experimental Design B/C

Postby Phys1cs » September 25th, 2014, 7:07 pm

Hey Heavyhitter!

So I've always been confused by that big complicated expression myself. Standard deviation is basically measure of how spread out your data values are.

Analyzed step by step:

1. Take the mean of the data. (Symbol is x with bar over it)
2. For each data point, subtract mean from the data point. Then square this difference.
3. Add up the squares.
4. Divide this sum by number of terms minus 1. (Symbol of number of terms is n.)
5. Take square root.

For example:

Data set: 1, 3, 5, 7, 9

1. Mean = 5
2 and 3. (1 minus 5)^2 + (3 minus 5)^2 + ... = 40
4. 40 divided by (5 minus 1) = 8
5. Square root of 8 = 2.828

Standard Deviation = 2.828


Note:If your data includes possible data points for a population, then in step 4 you would instead divide by the number of terms. But if you're working with a sample of the data, which is probably the case in XPD, you divide by number of terms minus 1.

Ex. If you're analyzing the height of ALL students in your grade level, then you divide by number of data values. If you analyze the height of a randomly selected, representative sample of students in your grade level, you divide by number of data values minus 1.

Alternatively, since you can calculate Standard Deviation on your Scientific/Graphing calculator. Plug data in Stat, and use 1-var stats. Standard deviation is round-greek symbol with line out.



Good luck :D
Standard deviation is somewhat different from other statistics needed for this event. Unlike the mean, which is an average (a reference number), or the range, (a specific reference point for data values), standard deviation is how much your data should deviate from the mean. Within +/- 3 standard deviations of the mean, (if your mean is 5 and your deviation 1, that would be from points 2 through 8) around 97% of your data should be there. It makes a nice bell curve, if your data is good. Something like 70 ish % should be one standard deviation away.

So be careful when explaining the significance of this particular stat

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Re: Experimental Design B/C

Postby Unome » September 26th, 2014, 4:18 am

Oh... I always did standard deviation without the squares.
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Re: Experimental Design B/C

Postby awesome90220 » September 30th, 2014, 11:28 am

Apart from the usual mean, median, mode, standard deviation, and line of best fit, what are some other statistics that might come in handy at the competition(divison b)
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Re: Experimental Design B/C

Postby HeavyHitter406 » October 7th, 2014, 8:04 pm

Apart from the usual mean, median, mode, standard deviation, and line of best fit, what are some other statistics that might come in handy at the competition(divison b)
I think they look for range (highest data value-lowest data value).
2014 (Wright State/Lisle/Grayslake/Regionals/State/Nationals)

Water Quality: 8/1/2/1/2/3
Experimental Design: 12/1/5/5/8/37
Road Scholar: 12/2/2/3/3/11
Wheeled Vehicle: 32/6/6/2/11/5

HeavyHitter406
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Re: Experimental Design B/C

Postby HeavyHitter406 » October 7th, 2014, 8:05 pm

Hey Heavyhitter!

So I've always been confused by that big complicated expression myself. Standard deviation is basically measure of how spread out your data values are.

Analyzed step by step:

1. Take the mean of the data. (Symbol is x with bar over it)
2. For each data point, subtract mean from the data point. Then square this difference.
3. Add up the squares.
4. Divide this sum by number of terms minus 1. (Symbol of number of terms is n.)
5. Take square root.

For example:

Data set: 1, 3, 5, 7, 9

1. Mean = 5
2 and 3. (1 minus 5)^2 + (3 minus 5)^2 + ... = 40
4. 40 divided by (5 minus 1) = 8
5. Square root of 8 = 2.828

Standard Deviation = 2.828


Note:If your data includes possible data points for a population, then in step 4 you would instead divide by the number of terms. But if you're working with a sample of the data, which is probably the case in XPD, you divide by number of terms minus 1.

Ex. If you're analyzing the height of ALL students in your grade level, then you divide by number of data values. If you analyze the height of a randomly selected, representative sample of students in your grade level, you divide by number of data values minus 1.

Alternatively, since you can calculate Standard Deviation on your Scientific/Graphing calculator. Plug data in Stat, and use 1-var stats. Standard deviation is round-greek symbol with line out.



Good luck :D
Thanks! I will have to look through a couple times to make sure I've got it, but seems legit! :]
2014 (Wright State/Lisle/Grayslake/Regionals/State/Nationals)

Water Quality: 8/1/2/1/2/3
Experimental Design: 12/1/5/5/8/37
Road Scholar: 12/2/2/3/3/11
Wheeled Vehicle: 32/6/6/2/11/5

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Re: Experimental Design B/C

Postby Panda Weasley » November 5th, 2014, 4:26 pm

Does anyone know if Division B people get bonus points for doing Standard Deviation? Also, does anyone have any pointers on how to get maximum points (and or bonus points)?
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Re: Experimental Design B/C

Postby XJcwolfyX » November 5th, 2014, 5:53 pm

Hi Panda! No, you do not receive extra credit or extra points for having Standard Deviation for Division B.

If you would like tips and hints about the event, please join us on the IRC Chat (Chat button on the top bar) or PM me! :)
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