# Answer: Probability That Mail Will Arrive Before Noon at Least One Day Wed/Thurs

• EvilPony
In summary, the conversation discusses the probability of mail being delivered before noon on Wednesday and Thursday. It is mentioned that there is an 80% chance for Wednesday and 40% chance for Thursday. The question is then raised about the probability of mail arriving before noon on at least one of those two days. The conversation then delves into discussing the use of the independent test and solving for the probability of none happening. The final answer suggested is 88% and the question is posed if it makes sense and if it should be greater than the individual day probabilities.
EvilPony
There is a 80% chance that Wednesday's mail will be delivered before noon on Wednesday and a 40% chance that Thursday's mail will be delivered before noon on Thursday. If these probabilities are independent, what is the probability that the mail will arrive before noon at least one of those two days?

What thoughts have you had so far?

heh guess I should be posting what I've done on these instead of just posting the question :)

ok well all I know is that its .8 (x) + .4 (x) , but I have no idea what the variable x is. I can't just add .8 and .4 because that would be greater then one. So i guess I just need help figuring out what x is

Well, why do you think that?

or maybe this has something to do with the independent test...

One way to go about solving "at least one" problems, is to think of the probability that none happen.

so 1-.2(.6)? which is 88% then?

Evilpony,

Does that answer (88%) seem to make sense? Should it be greater than the probability on either individual day?

## 1. What does "probability" mean in this context?

In this context, "probability" refers to the likelihood or chance that the mail will arrive before noon at least one day out of Wednesday and Thursday.

## 2. How is the probability calculated?

The probability is calculated by dividing the number of times the mail has arrived before noon on either Wednesday or Thursday by the total number of times the mail is expected to arrive on those two days.

## 3. What factors can affect the probability?

The probability can be affected by various factors such as weather conditions, transportation delays, and the efficiency of the postal service.

## 4. Is this probability accurate and reliable?

The accuracy and reliability of the probability depend on the data used to calculate it. If the data is collected over a long period of time, it can provide a more accurate and reliable estimate of the probability.

## 5. How can this probability be used?

This probability can be used to make decisions or predictions about the likelihood of the mail arriving before noon on either Wednesday or Thursday. It can also be used to identify any patterns or trends in the arrival time of mail on these two days.

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