A study of corporate business costs was conducted to find if there was difference between the average amount spent on dinner by executives and the average amount spent on dinner by managers. The mean for 32 executives was $25.50, with a standard deviation of $4.75. The mean for 35 managers was $22.50 with a standard deviation of $2.83.
If µ 1 is the mean for all executives and µ 2 is the mean for all managers, what is the 90% confidence interval of the true difference in the means?