Question 872802
					
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Hi
x	n	nx	x -2.85	n(x -2.85)^2	
1.45	6	8.7	-1.4	11.76	
2.45	7	17.15	-0.4	1.12	
3.45	2	6.9	0.6	0.72	
4.45	3	13.35	1.6	7.68	
5.45	2	10.9	2.6	13.52	
					
	20	57		34.8	
	mean	2.85		1.74	Variance
				1.32	SD
4. What percentage of the checkout times was at least 4 minutes? 5/20 = 25%
 5. Calculate the mean of this frequency distribution. 2.85
 6. Calculate the standard deviation of this frequency distribution. 
Variance = 1.74 (34.8/20) n used as divisor
SD = sqrt(1.74) = 1.32