A regression equation Y = a + bX is used to forecast the value of Y for a given value of X. Which of the following increase the reliability of the forecast? (i)
A、correlation coefficient numerically close to 1 (ii) Working to a higher number of decimal places of accuracy (iii) Forecasting for values of X outside the range of those used in the sample (iv)
A、large sample is used to calculate the regression equation
A、(i) only
B、(i) and (ii) only
C、(i) and (iii) only
D、(i) and (iv) only
A、correlation coefficient numerically close to 1 (ii) Working to a higher number of decimal places of accuracy (iii) Forecasting for values of X outside the range of those used in the sample (iv)
A、large sample is used to calculate the regression equation
A、(i) only
B、(i) and (ii) only
C、(i) and (iii) only
D、(i) and (iv) only
【参考答案及解析】
(i) A correlation coefficient close to +1 or -1 indicates a strong linear relationship between X and Y. The regressihe methods used lend themselves to such precision.(iii) Forecasting for values of X outside the range of the original data leads to unreliable estimates, because there is no evidence that the same regression relationships hold for such values.(iv) The regression equation is worthless unless a sufficiently large sample was used to calculate it. In practice, samples of about ten or more are acceptable.(i) and (iv) increase the reliability of forecasting.
(i) A correlation coefficient close to +1 or -1 indicates a strong linear relationship between X and Y. The regressihe methods used lend themselves to such precision.(iii) Forecasting for values of X outside the range of the original data leads to unreliable estimates, because there is no evidence that the same regression relationships hold for such values.(iv) The regression equation is worthless unless a sufficiently large sample was used to calculate it. In practice, samples of about ten or more are acceptable.(i) and (iv) increase the reliability of forecasting.