What Is the Help Variable in Swedish Regression Analysis?

[mathpariah]

Homework Statement

Ive two questions not directly relating to a problem but just stat in general.

i)
In Swedish what is called the "help variable" for a regression equation: y=u'*B where u' is the vector of explaining variables (x1,...,xn) can apparently be written in many ways..

One way is this:

($\bar{X}$-μ) / s*√(u$^{T}$(X$^{T}$X)$^{-1}$u)

OR

in some cases I've found its written:

($\bar{X}$-μ) / s*√(1 + u$^{T}$(X$^{T}$X)$^{-1}$u)

ii)

is variance s=√(μ/n)?

Homework Equations

What is the difference? It obviously affects the interval when you calculate it whether or not you have a 1 there or not.

The Attempt at a Solution

 

[lippyka]

i) In Swedish, the "help variable" for a regression equation is usually referred to as an "omhändertagande variabel". The difference between the two equations is that the first equation does not include a 1 in the denominator, while the second equation does. This means that the second equation will provide a more conservative estimate of the variance. ii) No, variance s is not equal to √(μ/n). Variance s is the standard deviation of a set of data and is calculated by taking the square root of the sum of the squared differences between each data point and the mean, divided by the number of data points.