You are investigating the stability of stock index returns over a multi-decade horizon. You collect the following information about monthly index returns:

Time	N. observations	Mean return (%)	St.Dev (%)
1990-1999	120	-0.07	3.61
2000-2009	120	0.08	3.4

Assuming equal variances between periods, calculate the statistic for differences between means, to test the hypothesis that the means are equal. Bonus thinking question: can you reject the equal means hypothesis? Enter answer accurate to 3 decimal places. PLEASE SHOW STEPS AND DO THE PROBLEM ON EXCEL.