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 Estimation
Famous quotes containing the words power and, power, sample, size and/or calculations:
“Cruelty is a mystery, and the waste of pain. But if we describe a word to compass these things, a world that is a long, brute game, then we bump against another mystery: the inrush of power and delight, the canary that sings on the skull.”
—Annie Dillard (b. 1945)
“No other human being, no woman, no poem or music, book or painting can replace alcohol in its power to give man the illusion of real creation.”
—Marguerite Duras (b. 1914)
“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)
“Delusions that shrink to the size of a woman’s glove,
Then sicken inclusively outwards:
. . . the incessant recital
Intoned by reality, larded with technical terms,
Each one double-yolked with meaning and meaning’s rebuttal:
For the skirl of that bulletin unpicks the world like a knot....”
—Philip Larkin (1922–1986)
“Nowhere are our calculations more frequently upset than in war.”
—Titus Livius (Livy)