how do you find point estimate for standard deviation?
1) The dashes are only here to keep the chart lined up. I posted this before and it didnt line up correctly.
2) Hopefully you're familiar with X bar. The three Xs have the bar (_) symbol above them. Hope this helps!
Make Chart First=
-----------------------(_)---------------(_)--------------(_)
--------xi--------------x------------ (xi-x)------------(xi-x)2
-------25-------------34--------------(-9)---------------81
-------32-------------34--------------(-2)----------------4
-------26-------------34--------------(-8)---------------64
-------40-------------34---------------6-----------------36
-------50-------------34--------------16---------------256
-------54-------------34--------------20----------------400
-------22-------------34-------------(-12)--------------144
-------23-------------34-------------(-11)-------------121
Total= 272--------------------Total= 0----- Total= 1106
Point estimate standard deviation of population :
The square root of:
*1106/ 8-1=
1106/7=
The square root of 158= 12.56980508997653471
* I do not know how to show the square root on here but for the equation the number of sample is variable n. For the bottom of the division problem it is (n-1), which makes it 8-1=7
So the point estimate standard deviation of population is 12.56980508997653471
the sample standard deviation
Not a lot. After all, the sample sd is an estimate for the population sd.
If the population standard deviation is sigma, then the estimate for the sample standard error for a sample of size n, is s = sigma*sqrt[n/(n-1)]
Standard error of the sample mean is calculated dividing the the sample estimate of population standard deviation ("sample standard deviation") by the square root of sample size.
No. Well not exactly. The square of the standard deviation of a sample, when squared (s2) is an unbiased estimate of the variance of the population. I would not call it crude, but just an estimate. An estimate is an approximate value of the parameter of the population you would like to know (estimand) which in this case is the variance.
The standard deviation of the population. the standard deviation of the population.
the sample standard deviation
Not a lot. After all, the sample sd is an estimate for the population sd.
If the population standard deviation is sigma, then the estimate for the sample standard error for a sample of size n, is s = sigma*sqrt[n/(n-1)]
From what ive gathered standard error is how relative to the population some data is, such as how relative an answer is to men or to women. The lower the standard error the more meaningful to the population the data is. Standard deviation is how different sets of data vary between each other, sort of like the mean. * * * * * Not true! Standard deviation is a property of the whole population or distribution. Standard error applies to a sample taken from the population and is an estimate for the standard deviation.
Standard error of the sample mean is calculated dividing the the sample estimate of population standard deviation ("sample standard deviation") by the square root of sample size.
Yes
No.
The standard deviation if the data is a sample from a population is 7.7115; if it is the population the standard deviation is 7.0396.
No. Well not exactly. The square of the standard deviation of a sample, when squared (s2) is an unbiased estimate of the variance of the population. I would not call it crude, but just an estimate. An estimate is an approximate value of the parameter of the population you would like to know (estimand) which in this case is the variance.
Yes.
There is 1) standard deviation, 2) mean deviation and 3) mean absolute deviation. The standard deviation is calculated most of the time. If our objective is to estimate the variance of the overall population from a representative random sample, then it has been shown theoretically that the standard deviation is the best estimate (most efficient). The mean deviation is calculated by first calculating the mean of the data and then calculating the deviation (value - mean) for each value. If we then sum these deviations, we calculate the mean deviation which will always be zero. So this statistic has little value. The individual deviations may however be of interest. See related link. To obtain the means absolute deviation (MAD), we sum the absolute value of the individual deviations. We will obtain a value that is similar to the standard deviation, a measure of dispersal of the data values. The MAD may be transformed to a standard deviation, if the distribution is known. The MAD has been shown to be less efficient in estimating the standard deviation, but a more robust estimator (not as influenced by erroneous data) as the standard deviation. See related link. Most of the time we use the standard deviation to provide the best estimate of the variance of the population.