In: Statistics and Probability
2) Basic Probability
Suppose a simple computer contains 16 memory sectors, 4 of which are read-only. We need to use 3 of the sectors.
A.) How many different samples are possible?
B.) Find the probability that none in the sample are read-only.
C.) Find the probability that exactly 2 registers in the sample are read-only.
D.) Find the probability that at least 1 sector is read-only
(a) The number of different possible sample may be given as the combination
(b) Since there are 4 read-only sectors, therefore the number of non read only sectors are (16-4)=12. Now the probability that all the 3 samples are selected from non read only sectors may be given by
that is there is 39.29% probability that there are no read only sectors selected in the sample.
(c) The required probability that there are exactly 2 read-only sectors are selected in the sample is given by
Hence there is 12.86% probability that there are exactly 2 read-only sectors are selected in the sample.
(d) If A represents the number of selected read only sector in the sample then the required probability may be represented as
Hence there is 25.36% probablity that there is at least 1 read-only sector is in the sample.