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.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
I think they look for range (highest data value-lowest data value).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)
Thanks! I will have to look through a couple times to make sure I've got it, but seems legit! :]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
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