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, sample, size and/or calculations:
“I talk democracy to these men and women. I tell them that they have the vote, and that theirs is the kingdom and the power and the glory. I say to them “You are supreme: exercise your power.” They say, “That’s right: tell us what to do;” and I tell them. I say “Exercise your vote intelligently by voting for me.” And they do. That’s democracy; and a splendid thing it is too for putting the right men in the right place.”
—George Bernard Shaw (1856–1950)
“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)
“Heaven’s calculations don’t follow man’s calculations.”
—Chinese proverb.