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:
“Coal lay in ledges under the ground since the Flood, until a laborer with pick and windlass brings it to the surface. We may will call it black diamonds. Every basket is power and civilization. For coal is a portable climate.”
—Ralph Waldo Emerson (1803–1882)
“The power of the past does not depend on our knowledge of it.”
—Mason Cooley (b. 1927)
“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 obvious places in which government can narrow the chasm between haves and have-nots. One is the public schools, which have been seen as the great leveler, the authentic melting pot. That, today, is nonsense. In his scathing study of the nation’s public school system entitled “Savage Inequalities,” Jonathan Kozol made manifest the truth: that we have a system that discriminates against the poor in everything from class size to curriculum.”
—Anna Quindlen (b. 1952)
“What, really, is wanted from a neighborhood? Convenience, certainly, an absence of major aggravation, to be sure. But perhaps most of all, ideally, what is wanted is a comfortable background, a breathing space of intermission between the intensities of private life and the calculations of public life.”
—Joseph Epstein (b. 1937)