Q-techniques

2001-01-24 Thread Paolo Covelli
I know that the techniques as principal component analysis, factor analysis or canonical correlation analysis are called R-techniques, because the correlation matrix R plays an important role in this approach. Instead techniques such as discriminant analysis, cluster analysis or multidimensional s

Re: standard deviation from frequency table

2001-01-10 Thread Paolo Covelli
Referring your example: variance = 2_nd moment - (1_st moment), that is: 2_nd moment = 0^2 * 0.2 + 1^2 * 0.3 + 2^2 * 0.2 + 3^2 * 0.2 + 4^2 * 0.1 = 4.5 1_st moment = 0 * 0.2 + 1 * 0.3 + 2 * 0.2 + 3 * 0.2 + 4 * 0.1 = 1.7 then variance = 4.5 - (1.7)^2 = 1.61 then standard deviation = sqrt(1.61) = 1.

Re: skewness

2000-12-30 Thread Paolo Covelli
Sorry, the exact formula is V=(x-mu)' sigma^{-1}(y-mu). However I have understand what you mean. Thank you, Paolo "Herman Rubin" <[EMAIL PROTECTED]> ha scritto nel messaggio 92koov$[EMAIL PROTECTED]">news:92koov$[EMAIL PROTECTED]... > In article <0OX26.738$

skewness

2000-12-29 Thread Paolo Covelli
Hi, let x, y be two i.i.d. N(mu, sigma) p_variate. How can I show that the distribution of V=(x-mu)' sigma^{-1}(x-mu), where sigma^{-1} is the inverse of co_variance matirx sigma, is symmetric? Thanks, Any help would be greatly appreciated. Paolo