Question

You ask a neighbor to water a sickly plant while you are on vacation. Without water the plant will die with probability 0.9. With water it will die with probability 0.55. You are 88 % certain the neighbor will remember to water the plant.

When you are on vacation, find the probability that the plant will die.

Answer:

You come back from the vacation and the plant is dead. What is the probability the neighbor forgot to water it?

Answer:

Answer 1

Answer:

Given that:

You ask a neighbor to water a sickly plant while you are on vacation.without water the plant will die with probability 0.9.with water it will die with probability 0.55.

Let's make a tree diagram to demonstrate this question.

Here, W is the event the plant is watered, and W' is the event it isn't watered. Furthermore, D is the event the plant dies, and L is the event the plant lives. Using the above diagram, we can answer these two questions.

Therefore, the probability the plant dies is the probability the plant is watered and dies plus the probability the plant is not watered and dies. This will be:

so there is a 59.2% chance the plant dies.

For the second part, we can use Bayes formula, which states that

so given the plant dies, there is a 18.24% chance that the neighbor forgot to water is.