Question 892769
Please help me solve this the distribution of the number of erros 10 students made on a typing test is shown. 
Errors Frequency 
0-2 1
 3-5 3
 6-8 4
 9-11 1
 12-14 1
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I'll work out the mean.  You can work out the standard deviation.
Note:: Use the mark of each interval to represent the interval value.
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mean = (1*1 + 3*4 + 4*7 + 1*10 + 1*13)/(1+3+4+1+1) 
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= (1 + 12 + 28 + 10 + 13)/(10)
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= 64/10
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= 6.4
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Note:: The answer you should get for the sample standard deviation is 3.41
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Cheers,
Stan H.
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