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.
Identifying and measuring bull markets is both art and science. One common measure says that a bull market exists when at least 80% of all stock prices rise over an extended period. Another measure says that a bull market exists if market indices rise at least +15%. Of course, different market sectors may experience bull markets at different times. The causes and characteristics of bull markets vary, but most financial theorists agree that both economic cycles and investor sentiment both play a role in the creation and momentum of bull markets.