Ms. Johnson uses a statistics program to analyze all the data collected by her students during a lab experiment about the acceleration due to gravity. The program reports a mean of 31.5 and a standard deviation of 2.5. What is the variance of the data? Round to the nearest tenth. A. 2.5 B. 5.6 C. 1.6 D. 6.3

The variance (σ^2) is the square of the differences between the mean and each data.
 The problem says that the program reports a mean of 31.5 and a standard deviation of 2.5, so you have to elevate the standar deviation to the power 2:

 σ^2 = (2.5)^2 
 σ^2 = 6.30       

 What is the variance of the data?
 The variance of the data is 6.30, so the the correct option is D.