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MBA 604 Introduction Probaility and Statistics Lecture Notes

MBA 604 Introduction Probaility and Statistics Lecture Notes

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s = √ s 2<br />

or s =<br />

Example: Same sample as before (x = 80)<br />

x x−x (x − x) 2<br />

90 10 100<br />

85 5 25<br />

65 -15 225<br />

75 -5 25<br />

70 -10 100<br />

95 15 225<br />

Totals 480 0 700<br />

Therefore<br />

s 2 =<br />

<br />

x<br />

x =<br />

n<br />

(x − x) 2<br />

n − 1<br />

(x−x) 2<br />

n−1<br />

= 480<br />

6 =80<br />

= 700<br />

5<br />

= 140<br />

s = √ s 2 = √ 140 = 11.83<br />

Shortcut Formula for Calculating s 2 <strong>and</strong> s<br />

Example: Same sample<br />

s 2 2 (<br />

x −<br />

=<br />

x) 2<br />

n<br />

n − 1<br />

<br />

<br />

<br />

<br />

<br />

x2 (<br />

−<br />

s =<br />

x) 2<br />

n<br />

n − 1<br />

(or s = √ s 2 ).<br />

13

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