How do I find the Standard Error of the Mean (SEM) and variance? Please help?
Posted on January 25, 2009
Filed Under Mathematics | 1 Comment
coolblue asked:
Hey everyone, I am having a hard time with doing my chemistry calculations. I think I understand how to find the SEM, but the variance confuses me. (Like, how do you get the number in front of your value that has a + or – above one another) Thanks a lot for the help and I really appreciate it.
time management
Hey everyone, I am having a hard time with doing my chemistry calculations. I think I understand how to find the SEM, but the variance confuses me. (Like, how do you get the number in front of your value that has a + or – above one another) Thanks a lot for the help and I really appreciate it.
time management
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time management
SEM = standard deviation divided by the square root of n, where n is the sample size. Variance is the square of the standard deviation.
If the variance is 64, for example, the standard deviation is 8.
If you have a set of data, you can compute the mean and the standard deviation.
Here is an example.
The data : 4,6,8,10
Number of cases 4
To find the mean, add all of the observations and divide by 4
Mean 7
Squared deviations
(4-7)^2 = (-3)^2 = 9
(6-7)^2 = (-1)^2 = 1
(8-7)^2 = (1)^2 = 1
(10-7)^2 = (3)^2 = 9
Add the squared deviations and divide by 4
Variance = 20/4
Variance 5
Standard deviation = sqrt(variance) = 2.2361
SEM = 2.2361 / 2 =1.11805