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 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)
“Speak, nameless, power and might;
when will you leave me quite?
when will you break my wings
or leave them utterly free
to scale heaven endlessly?”
—Hilda Doolittle (1886–1961)
“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)
“To believe her limited in range because she was harmonious in method is as sensible as to imagine that when the Atlantic Ocean is as smooth as a mill-pond it shrinks to the size of a mill-pond.”
—Rebecca West (1892–1983)
“The vulgar call good fortune that which really is produced by the calculations of genius.”
—Ralph Waldo Emerson (1803–1882)