Six different second-year medical students at Bellevue Hospital measured the blo

Question

Six different second-year medical students at Bellevue Hospital measured the blood pressure of the same person. The systolic readings (in mmHg) are listed below. Find the range, variance, and standard deviation for the given sample data. If the subject's blood pressure remains constant and the medical students correctly apply the same measurement technique, what should be the value of the standard deviation?

138 142 123 144 126 140

what is the range           mmHg

Explanation / Answer

Ordering the data,

123
126
138
140
142
144

Also, we have          
          
Maximum =    144      
Minimum =    123      

Range = max - min =    21   [ANSWER, RANGE]

*******************************************  

Getting the mean, X,          
          
X = Sum(x) / n          
Summing the items, Sum(x) =    813      
As n =    6      
Thus,          
X =    135.5      
          
Setting up tables,          
x   x - X   (x - X)^2  
123   -12.5   156.25  
126   -9.5   90.25  
138   2.5   6.25  
140   4.5   20.25  
142   6.5   42.25  
144   8.5   72.25  
          
Thus, Sum(x - X)^2 =    387.5      
          
Thus, as           
          
s^2 = Sum(x - X)^2 / (n - 1)          
          
As n =    6      
          
s^2 =    77.5   [ANSWER, VARIANCE]  
          
Thus,          
          
s =    8.803408431   [ANSWER, STANDARD DEVIATION]  
          

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