the arithmetic mean of set x is zero . if y = { - 2.22 ; - 1.96 ; - 1.68 ; 1.62 ; 1.94 ; 2.16 } is the subset of x consisting of all those elements in x which are more than two but less than 3 standard deviations away from the arithmetic mean of x , what could be equal to the standard deviation of x ? Options:
A) 0.54
B) 0.77
C) 0.82
D) 0.97
E) 1.62

Rationale: this is a fairly straightforward question that can be solved quickly by just applying the options we are provided with mean , m = 0 and y = { - 2.22 ; - 1.96 ; - 1.68 ; 1.62 ; 1.94 ; 2.16 } is the subset of s y consists of all those elements in x that are more than 2 but less than 3 xds away from the arithmetic mean of x if an element is 1 xd away from the mean , we can write it as either m + xd or m - xd similarly , if an element is 2 xds away from the mean , we can write it as either m + 2 * xd or m - 2 * xd so , if these elements lie within 2 and 3 xds of mean , m = 0 we can find which one of these values of xd satisfies each value within y only xd = 0.77 does answer : b
Answer: B