Mrs. rodrigues wants to compare the spread of the test scores of her two biology classes. which statistic should she use? -mean -standard deviation -median -mode

Standard deviation

Step-by-step explanation:

Mean, median, and mode are three kinds of "averages".

The "mean" is the "average" is where you add up all the numbers and then divide by the number of numbers. The "median" is the "middle" value in the list of numbers. To find the median, your numbers have to be listed in numerical order from smallest to largest, so you may have to rewrite your list before you can find the median. The "mode" is the value that occurs most often. If no number in the list is repeated, then there is no mode for the list.

All these do not mention about the spread of the data.

But std deviation is the square root of variance.  Variance is the sum of squares of deviations from mean of each entry.  Hence to learn spread std deviation is the best measure.