The answer is EEEEEEEEE

 

2.5%, that's the key.

I think the answer is 10. 95% of the population will be in the 2 SD straddling the mean...so 2.5% will remain on each side of that 95% distribution.

Hence the answer = 2.5/100 * 400 = 10.

I am surprised that one of the options is not 20, that would have been picked if you forgot that it was 2.5% not 5%.

I hope this helps.

 

my answer

I agree - (E) 10

 

Of course 10 will be the straight choice but if ans had option 20 than ?
The question said two SD above that leaves 5% ?

 

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I'm not sure if I understand...
But if the question says 2 SD above it leaves us with 2,5%.
2 SD below and 2 SD above would give 5%.

 

Well that is my question 2 SD above is 3rd SD that aprox 5% .
If 10 is the answer expected than language wrong or this is the format used for SD questions ??

 

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There's nothing wrong with this question!
If this is 2 SD above it's 2,5% NOT 5%.

Take a look at the chart here: http://www.google.pl/imgres?imgurl=...s0=&docid=LcaoaG_-3hc1RM&sa=X&ei=vgYeUIzsDNHEsgaFsYGYCA&ved=0CHoQ9QEwAg&dur=155

2 SD above is 2,5% (in the pic they say it's 2,1% but ignore this difference) bc you're looking at what is to the right of the 2 SD line.

if you take a look at what is to the left of -2 SD you will see another 2,5%.
SO when you sum it up it gives you 5%. But only when you sum it up! Not when you read one side of the chart only.