Step 1 :Given the salaries of high school counselors in the United States, we are asked to construct a 99% confidence interval for the mean salary.
Step 2 :The given salaries are: \$63670, \$35250, \$61780, \$32370, \$32290, \$60250, \$60590.
Step 3 :First, we calculate the mean and standard deviation of the given salaries. The mean is \$49457.14 and the standard deviation is \$14055.04.
Step 4 :Next, we use the formula for the confidence interval which is mean ± (z-score * (standard deviation / sqrt(n))), where n is the number of samples, and the z-score for a 99% confidence interval is approximately 2.576.
Step 5 :Substituting the values into the formula, we get the margin of error as \$13683.59.
Step 6 :Finally, we subtract and add the margin of error from the mean to get the lower and upper endpoints of the confidence interval respectively.
Step 7 :The lower endpoint is \$35774 and the upper endpoint is \$63141.
Step 8 :So, the 99% confidence interval for the mean salary of high school counselors across the United States is \(\boxed{[\$35774, \$63141]}\).