Power and Sample Size Calculations
There are no generally agreed methods for relating the number of observations versus the number of independent variables in the model. One rule of thumb suggested by Good and Hardin is, where is the sample size, is the number of independent variables and is the number of observations needed to reach the desired precision if the model had only one independent variable. For example, a researcher is building a linear regression model using a dataset that contains 1000 patients . If he decides that five observations are needed to precisely define a straight line, then the maximum number of independent variables his model can support is 4, because
.
Read more about this topic: Regression Analysis
Famous quotes containing the words power and, power, sample, size and/or calculations:
“It feels good because God has power and if one does as God does enough times, one will become as God is.”
—Michael Mann, U.S. screenwriter. Hannibal Lechtor (Brian Cox)
“The power of this experience [fatherhood] can never be explained. It is one of those joyful codings that rumbles in the species far below understanding. When it is experienced it makes you one with all men in a way that fills you with warmth and harmony.”
—Kent Nerburn (20th century)
“As a rule they will refuse even to sample a foreign dish, they regard such things as garlic and olive oil with disgust, life is unliveable to them unless they have tea and puddings.”
—George Orwell (1903–1950)
“In mathematics he was greater
Than Tycho Brahe, or Erra Pater:
For he, by geometric scale,
Could take the size of pots of ale;
Resolve, by sines and tangents straight,
If bread and butter wanted weight;
And wisely tell what hour o’ th’ day
The clock doth strike, by algebra.”
—Samuel Butler (1612–1680)
“The vulgar call good fortune that which really is produced by the calculations of genius.”
—Ralph Waldo Emerson (1803–1882)