What is the standard deviation of the following data set rounded to the nearest tenth?78, 90, 456, 676, 111, 381, 21A.229.2B.229.1C.259D.258

  Note that the mean (78 +90 +456 +676 + 111+ 381+ 21)/7 = 259 
The differences (in absolute value - we're going to square later so it doesn't matter) between each piece of data and the mean are 
181, 169, 197, 417, 148, 122, 238 
Square each of these and add the results together to obtain 367452 
Now your question depends on whether you want the sample standard deviation or population standard deviation - which you have not specified. In the first case divide by 6. In the second case divide by 7. We get roughly 61242 or 52493. The square root of each yields 247.47 or 229.11 depending on whether you want the sample sd or pop sd. The 4 choices imply you are looking for the latter, so the answer is A.i think