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by danjuma » Sun Oct 10, 2010 9:25 am
70, 75, 80, 85, 90, 105, 105, 130, 130, 130.

The lists above consists of the times in seconds , it took each of 10 children to run a distance of 400m. If the standard deviation of the times is 22.4s, how many of the 10 running times are more than 1 standard deviation below the mean

a.1 b.2 c.3 d.4 e.5
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by this_time_i_will » Sun Oct 10, 2010 9:38 am
danjuma wrote:70, 75, 80, 85, 90, 105, 105, 130, 130, 130.

The lists above consists of the times in seconds , it took each of 10 children to run a distance of 400m. If the standard deviation of the times is 22.4s, how many of the 10 running times are more than 1 standard deviation below the mean

a.1 b.2 c.3 d.4 e.5
the mean for above 10 items = 100.
the range of i std. deviation is: 100-22.4 to 100+22.4 = 77.6 to 122.4

Items out of this range = 70, 75, 130,130,130

so a total of 5. E.
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by uwhusky » Sun Oct 10, 2010 9:49 am
https://www.beatthegmat.com/standard-dev ... 68152.html

We just had this discussion actually.
Yep.
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by this_time_i_will » Sun Oct 10, 2010 9:54 am
uwhusky wrote:https://www.beatthegmat.com/standard-dev ... 68152.html

We just had this discussion actually.
thanks for the link.
I see my mistake. sud have read the word below carefully.
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