Here Are the Average Mathematics Achievement Scores for Ninth Graders

Multiple Choice

Here are the average mathematics achievement scores for ninth graders in 34 counties.Find the standard deviation. $$\begin{array} { l l l l l l l l l } 595 & 588 & 587 & 586 & 582 & 580 & 561 & 555 & 551 \\548 & 542 & 540 & 538 & 537 & 534 & 532 & 524 & 523 \\515 & 512 & 501 & 498 & 493 & 489 & 485 & 483 & 465 \\462 & 458 & 444 & 435 & 431 & 407 & 380 & &\end{array}$$

A) 55.8
B) 57.5
C) 54.2
D) 56.2
E) 55.2