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:
“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)
“The importance of a lost romantic vision should not be underestimated. In such a vision is power as well as joy. In it is meaning. Life is flat, barren, zestless, if one can find one’s lost vision nowhere.”
—Sarah Patton Boyle, U.S. civil rights activist and author. The Desegregated Heart, part 1, ch. 19 (1962)
“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)
“It is very considerably smaller than Australia and British Somaliland put together. As things stand at present there is nothing much the Texans can do about this, and ... they are inclined to shy away from the subject in ordinary conversation, muttering defensively about the size of oranges.”
—Alex Atkinson, British humor writer. repr. In Present Laughter, ed. Alan Coren (1982)
“Heaven’s calculations don’t follow man’s calculations.”
—Chinese proverb.