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:
“I should fear the infinite power and inflexible justice of the almighty mortal hardly as yet apotheosized, so wholly masculine, with no sister Juno, no Apollo, no Venus, nor Minerva, to intercede for me, thumoi phileousa te, kedomene te.”
—Henry David Thoreau (1817–1862)
“When there is sympathy, there needs but one wise man in a company and all are wise,—so, a blockhead makes a blockhead of his companion. Wonderful power to benumb possesses this brother.”
—Ralph Waldo Emerson (1803–1882)
“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)
“The obese is ... in a total delirium. For he is not only large, of a size opposed to normal morphology: he is larger than large. He no longer makes sense in some distinctive opposition, but in his excess, his redundancy.”
—Jean Baudrillard (b. 1929)
“Heaven’s calculations don’t follow man’s calculations.”
—Chinese proverb.