Question

1.  Fourteen percent of workers believe they will need less than $250,000 when they retire. You randomly select 10 workers and ask them how much money they think they will need for retirement. Find the probability that the number of workers who say they will need less than $250,000 when they retire is:

1. a)  more than six.

b)  between two and four, including two and four.

Answer 1

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p	0.14
q	0.86
n	10
	r	(n-r)	p^r	q^(n-r)	nCr	P(X = r)
	0	10	1	0.221302	1	0.221302
	1	9	0.14	0.257327	10	0.360258
	2	8	0.0196	0.299218	45	0.26391
	3	7	0.002744	0.347928	120	0.114566
	4	6	0.000384	0.404567	210	0.032638
	5	5	5.38E-05	0.470427	252	0.006376
	6	4	7.53E-06	0.547008	210	0.000865
	7	3	1.05E-06	0.636056	120	8.05E-05
	8	2	1.48E-07	0.7396	45	4.91E-06
	9	1	2.07E-08	0.86	10	1.78E-07
	10	0	2.89E-09	1	1	2.89E-09
					Sum	1