I am doing regression for dependent variable Y and independent variables X1, X2, X3 and X4. Y is the weekly stock price of a company which does gold mining, processing and selling business. This company is listed in Shanghai Stock Exchange. X1 ~ X3 are the gold futures prices traded in New York, in Shanghai and US$ index. X4 is the broad market index. The correlation coefficient between X1,x2,x3,x4 with Y respectively is about 50%~60%. The number of observations are 28. The confidence level is 95%. I regressed the 5 variables, the R-square is about 47%, which is understandable, but each of the four independent variables (X1~X4) are statistically insignificant (p-value > 0.05). I don't understand. Can anyone here explain?

Thanks so much for help!

2008-8-4