I. When the sum of the residuals is greater than zero, the data set is nonlinear. II. A random pattern of residuals supports a linear model. III. A random pattern of residuals supports a non-linear model.
bull market definition. A market, especially a stock market, characterized by rising prices; the opposite of a bear market. We can always go back to worrying; we are still in a bull market for fear.
A bear market is the opposite of a bull market. It's a downward trend or a falling market. Investors are less likely to invest their money and don't exhibit buying confidence. In fact, they are more inclined to sell their shares. A good example from history is the stock market crash of 1929, leading into the Great Depression.