topic Re: Number of observations used for calculating STD in Statistical Procedures https://communities.sas.com/t5/Statistical-Procedures/Number-of-observations-used-for-calculating-STD/m-p/128824#M6755 <HTML><HEAD></HEAD><BODY><P>The standard deviation is already adjusted for the number of observations. That's why it is called the "standard" (-ized) deviation (from the mean).&nbsp; The only thing that you need to be aware of for interpretation is that there are two ways that someone can have a big standard deviation: (1) they can have moderate variablity but a small number of observations (such as 3), or (2) they can have a lot of variability with a large number of observatios (such as 10).</P></BODY></HTML> Tue, 29 May 2012 23:11:29 GMT Rick_SAS 2012-05-29T23:11:29Z Number of observations used for calculating STD https://communities.sas.com/t5/Statistical-Procedures/Number-of-observations-used-for-calculating-STD/m-p/128823#M6754 <HTML><HEAD></HEAD><BODY><P>I have a dataset which contains multiple blood pressure measurements per patient. The issue is, that some patients may only have 3 blood pressure measurements while other will have 10 blood pressure measurements. I want to calculate the standard deviation of all a patients blood pressure measurements within a given month - does one patient having only 3 versus another patient have 10 blood pressure measurements in a month affect how I will interpret the STD of blood pressure per month?&nbsp; If I have not explained this clearly, please let me know. Thank you. </P></BODY></HTML> Tue, 29 May 2012 22:19:43 GMT https://communities.sas.com/t5/Statistical-Procedures/Number-of-observations-used-for-calculating-STD/m-p/128823#M6754 HyunJee 2012-05-29T22:19:43Z Re: Number of observations used for calculating STD https://communities.sas.com/t5/Statistical-Procedures/Number-of-observations-used-for-calculating-STD/m-p/128824#M6755 <HTML><HEAD></HEAD><BODY><P>The standard deviation is already adjusted for the number of observations. That's why it is called the "standard" (-ized) deviation (from the mean).&nbsp; The only thing that you need to be aware of for interpretation is that there are two ways that someone can have a big standard deviation: (1) they can have moderate variablity but a small number of observations (such as 3), or (2) they can have a lot of variability with a large number of observatios (such as 10).</P></BODY></HTML> Tue, 29 May 2012 23:11:29 GMT https://communities.sas.com/t5/Statistical-Procedures/Number-of-observations-used-for-calculating-STD/m-p/128824#M6755 Rick_SAS 2012-05-29T23:11:29Z