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:
“Do not say to yourself, “My power and the might of my own hand have gotten me this wealth.” But remember the LORD your God, for it is he who gives you power to get wealth, so that he may confirm his covenant that he swore to your ancestors, as he is doing today.”
—Bible: Hebrew, Deuteronomy 8:17,18.
“and men strive with each other not for power or the accumulation of paper
but in joy create for others the house, the poem, the game of
athletic beauty.
Then washed in the brightness of the vision,
I saw how in its radiance would grow and be nourished and suddenly
burst into terrible and splendid bloom
the blood-red flower of revolution.”
—Dudley Randall (b. 1914)
“The present war having so long cut off all communication with Great-Britain, we are not able to make a fair estimate of the state of science in that country. The spirit in which she wages war is the only sample before our eyes, and that does not seem the legitimate offspring either of science or of civilization.”
—Thomas Jefferson (1743–1826)
“There are some persons we could not cut down to size without diminishing ourselves as well.”
—Jean Rostand (1894–1977)
“Nowhere are our calculations more frequently upset than in war.”
—Titus Livius (Livy)