Question

Explain the difference between finding the probability when an object is replaced, and finding the probability when an object is NOT replaced.

Answer 1

Assume you have a bag containing 3 blue marbles & 2 red marbles

Suppose the event is to pick one red marble.

The probability of choosing one red marble =2/5 = 0.4

If you replace it in the bag & I ask you the probability of getting a red marble you will see that P(red marble) is always 2/5 = 0.4

Now if for the 2nd draw you dont replace it & I ask again the P(red), you will notice there is one red marble less & the P(red) on the second draw will be
P(red (2nd draw) = 1/4 (since the remaining in the bag are 1 Red & 3 Blues.