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

 

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