Your colleague at work was gathering some data for you,

Your colleague at work was gathering some data for you, and you noticed that she accidentally estimated the standard deviation as the square root of the average of the sum of the squared deviations from the sample mean (i.e., she "divided by n"). Her estimate was 270 for the 15 observations she collected. You wish to use an unbiased estimate of the sample variance. What is it ( show your work)?