## Experimental Design B/C

Jim_R Posts: 283
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### Experimental Design B/C

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HeavyHitter406
Member Posts: 45
Joined: April 13th, 2014, 5:50 pm
Division: C
State: IL

### Re: Experimental Design B/C

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
Wheeled Vehicle: 32/6/6/2/11/5

actionpotential
Member Posts: 12
Joined: September 25th, 2014, 5:15 pm
Division: C

### Re: Experimental Design B/C

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.
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 Phys1cs
Member Posts: 129
Joined: November 10th, 2013, 6:53 pm
State: MD

### Re: Experimental Design B/C

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.
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 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

Unome
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### Re: Experimental Design B/C

Oh... I always did standard deviation without the squares.
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awesome90220
Member Posts: 158
Joined: March 10th, 2012, 5:19 pm
Division: B
State: AL
Location: somewhere on this cruel, harsh planet

### Re: Experimental Design B/C

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)
2016 Season: BISOT/Reg/State/Nats
Wind Power:9/1/1/11
Experimental Design:5/1/1/16

HeavyHitter406
Member Posts: 45
Joined: April 13th, 2014, 5:50 pm
Division: C
State: IL

### Re: Experimental Design B/C

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
Wheeled Vehicle: 32/6/6/2/11/5

HeavyHitter406
Member Posts: 45
Joined: April 13th, 2014, 5:50 pm
Division: C
State: IL

### Re: Experimental Design B/C

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.
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 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
Wheeled Vehicle: 32/6/6/2/11/5

Panda Weasley
Member Posts: 133
Joined: September 27th, 2014, 6:24 am
Division: C
Location: Ravenclaw Tower

### Re: Experimental Design B/C

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)?
DFTBA!
Events 2019: Forensics and Fossils
Proud member of Teh Ento Cult. XJcwolfyX
Member Posts: 340
Joined: October 22nd, 2010, 7:57 am
Division: C

### Re: Experimental Design B/C

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! Medal Counter: 73