How to calculate standard deviation from mean and probability?
$begingroup$
What's the formula to calculate the standard deviation knowing the mean and a certain probability, but not knowing all the n's.
http://stattrek.com/online-calculator/normal.aspx
For example, ^that calculator only requires mean and a probability of Z to calculate the mean... so how does it do that? What's the formula? And how can I do it by myself in a CAS software during an exam?
standard-deviation
asked Apr 1 '14 at 22:12
JohnJohn
1112
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add a comment |
$begingroup$
What's the formula to calculate the standard deviation knowing the mean and a certain probability, but not knowing all the n's.
http://stattrek.com/online-calculator/normal.aspx
For example, ^that calculator only requires mean and a probability of Z to calculate the mean... so how does it do that? What's the formula? And how can I do it by myself in a CAS software during an exam?
standard-deviation
asked Apr 1 '14 at 22:12
JohnJohn
1112
$endgroup$
1
$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52
add a comment |
$begingroup$
What's the formula to calculate the standard deviation knowing the mean and a certain probability, but not knowing all the n's.
http://stattrek.com/online-calculator/normal.aspx
For example, ^that calculator only requires mean and a probability of Z to calculate the mean... so how does it do that? What's the formula? And how can I do it by myself in a CAS software during an exam?
standard-deviation
asked Apr 1 '14 at 22:12
JohnJohn
1112
$endgroup$
What's the formula to calculate the standard deviation knowing the mean and a certain probability, but not knowing all the n's.
http://stattrek.com/online-calculator/normal.aspx
For example, ^that calculator only requires mean and a probability of Z to calculate the mean... so how does it do that? What's the formula? And how can I do it by myself in a CAS software during an exam?
standard-deviation
standard-deviation
asked Apr 1 '14 at 22:12
JohnJohn
1112
asked Apr 1 '14 at 22:12
JohnJohn
1112
asked Apr 1 '14 at 22:12
JohnJohn
1112
asked Apr 1 '14 at 22:12
JohnJohn
1112
asked Apr 1 '14 at 22:12
JohnJohn
1112
1112
1
$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52
add a comment |
1
$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52
1
1
$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52
$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52
add a comment |
1 Answer
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$begingroup$
The formula for standard deviation is sqrt([sample size][probability of success](1-[probability of success])). To find the sample size from the mean and success rate, you divide the mean by the success rate. If mean=10 and success=0.2, you do 10/0.2 to get your sample size, or 50 in this case. Then you do sqrt(50*0.2*(1-0.2) to get about 2.83. There you go!
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
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1 Answer
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$begingroup$
The formula for standard deviation is sqrt([sample size][probability of success](1-[probability of success])). To find the sample size from the mean and success rate, you divide the mean by the success rate. If mean=10 and success=0.2, you do 10/0.2 to get your sample size, or 50 in this case. Then you do sqrt(50*0.2*(1-0.2) to get about 2.83. There you go!
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
$endgroup$
add a comment |
$begingroup$
The formula for standard deviation is sqrt([sample size][probability of success](1-[probability of success])). To find the sample size from the mean and success rate, you divide the mean by the success rate. If mean=10 and success=0.2, you do 10/0.2 to get your sample size, or 50 in this case. Then you do sqrt(50*0.2*(1-0.2) to get about 2.83. There you go!
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
$endgroup$
add a comment |
$begingroup$
The formula for standard deviation is sqrt([sample size][probability of success](1-[probability of success])). To find the sample size from the mean and success rate, you divide the mean by the success rate. If mean=10 and success=0.2, you do 10/0.2 to get your sample size, or 50 in this case. Then you do sqrt(50*0.2*(1-0.2) to get about 2.83. There you go!
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
$endgroup$
The formula for standard deviation is sqrt([sample size][probability of success](1-[probability of success])). To find the sample size from the mean and success rate, you divide the mean by the success rate. If mean=10 and success=0.2, you do 10/0.2 to get your sample size, or 50 in this case. Then you do sqrt(50*0.2*(1-0.2) to get about 2.83. There you go!
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
answered Apr 17 '14 at 4:22
PlatypusVenomPlatypusVenom
285
285
add a comment |
add a comment |
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$begingroup$
This the normal distribution and it has a known probability function and a standard table, it is a different case.
$endgroup$
– Semsem
Apr 1 '14 at 22:52