70,75, 73,76,90,105,105,130,130,130
The list consists of the times in seconds that it took each of the 10 school children to run a distance of 400 mts . If the standard deviation of the 10 running times is 22.4, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times.	Select the correct option.
A) 1
B) 2
C) 3
D) 4
E) 5
How many of the 10 running times are more than one SD below the meanmeans how many data points from given 10 are less thanmean-1SD.   We are given that SD=22.4, so we should find mean --&gt; mean=100 --&gt; there are only 3 data points below  100-22.4= 
<gadget id="calculator"> 100-22.4</gadget>
<output>77.6</output>
77.6, namely 70, 73 and 75.   Answer: 3.
<result>C</result>
70,75, 73,76,90,105,105,130,130,130
The list consists of the times in seconds that it took each of the 10 school children to run a distance of 400 mts . If the standard deviation of the 10 running times is 22.4, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times.