Question

There are 100 folders on your computer, with 10 videos per folder. The random choose function selects random video and play, and does this again and again(repeats the function). Every videos are 5 minutes .

(a) Find the probability of your computer plays two or more videos from the same folder in the next 1 hour?

(b) Find the probability of your computer plays two or more videos from the same folder in the next 2 hours?

(c) What are the anticipated number videos until your computer plays 2 videos from the same folder?

Answer 1

a)

Sample size , n =    12
Probability of an event of interest, p =   0.01

	X	P(X)
P ( X = 0) = C (12,0) * 0.01^0 * ( 1 - 0.01)^12=	0	0.8864
P ( X = 1) = C (12,1) * 0.01^1 * ( 1 - 0.01)^11=	1	0.1074

Probability that out of 12 videos folder used less than 2 times = 0.9938

Probability required = 1- 0.9938

= 0.0062

b)

Sample size , n =    24
Probability of an event of interest, p =   0.01

	X	P(X)
P ( X = 0) = C (24,0) * 0.01^0 * ( 1 - 0.01)^24=	0	0.7857
P ( X = 1) = C (24,1) * 0.01^1 * ( 1 - 0.01)^23=	1	0.1905

Probability required = 1- 0.9761

= 0.0239

c)

np = 100 * 0.01 = 1 folder

Anticipated Number = 101 videos

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