When standard deviation is undefined?

[socrates_1]

Hi, I just solved a probability density function problem and the standard deviation is undefined.Does anyone know why it happens?It would help to develop my understanding.Thanks.

 

[Number Nine]

Since you provided no details about the problem or the distribution you derived, it's hard for anyone to comment. Do you mean that the integral diverges when you try to calculate the variance? That's not unusual; there are a number of distributions lacking finite variance (see: Cauchy distribution).

 

[socrates_1]

Since you provided no details about the problem or the distribution you derived, it's hard for anyone to comment. Do you mean that the integral diverges when you try to calculate the variance? That's not unusual; there are a number of distributions lacking finite variance (see: Cauchy distribution).

Thank you very much for your response.The probability density function is given by :
f(x)= 24/x^3

When I try to calculate ∫ (x^2) f(x) - (m^2) is undefined.Why this is so?

 

[micromass]

Thank you very much for your response.The probability density function is given by :
f(x)= 24/x^3

That's not a valid density function. Are there any restrictions on x that you are forgetting to tell us?

 

[blue_raver22]

There are a few reasons why the standard deviation may be undefined in a probability density function problem. One possibility is that the sample size is too small, which can result in a lack of variability in the data. Another possibility is that the data is skewed or has extreme outliers, which can also affect the calculation of the standard deviation. Additionally, if the data is not normally distributed, the standard deviation may not be a meaningful measure of variability. It is important to consider the underlying assumptions and characteristics of the data when interpreting the results of a standard deviation calculation.