Geometric Distribution Problem Clarification

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Discussion Overview

The discussion revolves around a geometric distribution problem related to the probability of a driver being seriously injured in a car crash over a specified time period. Participants explore the implications of the given probability, the independence of events, and the expected value calculations in the context of this scenario.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant calculates the probability of being seriously injured at least once in a year using the formula for geometric distribution, suggesting a probability of approximately 0.6989866.
  • Another participant questions whether the driver is an average driver and whether the probability of a crash is independent for each hour, indicating these assumptions need clarification.
  • There is confusion regarding the correct formula for expected value, with participants discussing two different expressions: \text{Expected val }= \frac{1}{p} and \frac{1-p}{p}.
  • Participants emphasize the importance of clearly stating assumptions about independence and the nature of the driver in the problem to ensure the accuracy of the calculations.
  • One participant expresses uncertainty about whether their probability value is correct and seeks validation of their solution.

Areas of Agreement / Disagreement

Participants generally agree on the need for clarity regarding assumptions, particularly about the independence of events and the nature of the driver. However, there is no consensus on the correctness of the initial solution or the expected value calculations, as participants express differing views on these aspects.

Contextual Notes

Participants note the importance of assumptions in the problem, including the independence of crash probabilities and the characterization of the driver, which are not explicitly stated in the problem description.

Who May Find This Useful

This discussion may be useful for individuals interested in probability theory, particularly in understanding geometric distributions and the implications of assumptions in probabilistic models.

knowLittle
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TL;DR
I some hints or confirmation if my solution is correct.
I am bit confused about different formulas I have found involving geometric distribution.
And functions from R-language.
(Geometric). The probability of being seriously injured in a car crash in an unspecified location is about .1% per hour. A driver is required to traverse this area for 1200 hours in the course of a year. What is the probability that the driver will be seriously injured during the course of the year? In the course of 15 months? What is the expected number of hours that a driver will drive before being seriously injured? Given that a driver has driven 1200 hours, what is the probability that he or she will be injured in the next 100 hours?What is the probability that the driver will be seriously injured during the course of the year?
<br /> \text{This means what is the probability that the person gets seriously injured at least once in a year.}<br />

<br /> P(\text{at least one success}) = 1 - P(\text{failure in one trial})^n<br />

<br /> \text{In the formula above, n represents the total number of trials.}<br />

<br /> \text{We will be cruel and label an accident as a success.}<br />

<br /> 1 - (1 - \frac{.1}{100})^{1200} = 0.6989866<br /> <br />

prob of accident is p=.1/100 = 0.001
prob of non-accident is non_accident = 1-p

Would this answer be correct?
 
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The idea is correct, but there are some things that you should get in the habit of watching for.
knowLittle said:
(Geometric). The probability of being seriously injured in a car crash in an unspecified location is about .1% per hour. A driver
Is this an average driver with the average probability of a crash?
knowLittle said:
is required to traverse this area for 1200 hours in the course of a year. What is the probability that the driver will be seriously injured during the course of the year?
Are the odds of a crash on each hour independent of each other?
I believe that these are aspects that you should make some clear statements about to make your equation correct.
 
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FactChecker said:
The idea is correct, but there are some things that you should get in the habit of watching for.

Is this an average driver with the average probability of a crash?
I think I lack the intuition. I assume it's an average driver with an average probability, yes.

Does it mean that my p value is wrong?
I am confused about this different values for mean :
\text{Expected val }= \frac{1}{p}
or
\frac{1-p}{p}
?
FactChecker said:
Are the odds of a crash on each hour independent of each other?
I believe that these are aspects that you should make some clear statements about to make your equation correct.
The odds of crashing each hour are independent according to the problem description.
 
knowLittle said:
I think I lack the intuition. I assume it's an average driver with an average probability, yes.
That is the kind of thing that you should clearly state. And be careful if the problem doesn't state it.
knowLittle said:
Does it mean that my p value is wrong?
I am confused about this different values for mean :
\text{Expected val }= \frac{1}{p}
or
\frac{1-p}{p}
?
It's ok if you clearly state that the person you are talking about has that probability.
knowLittle said:
The odds of crashing each hour are independent according to the problem description.
Nothing that I see says that, especially for one person doing all the driving. It would be a natural assumption, but it is better if you state it clearly.
Suppose that one person who drives through safely a thousand times would tend to get careless? That is a very real-world situation. I am not trying to be picky, I am just trying to encourage you to specifically state if you are assuming some probabilities are independent (and/or to question that assumption). These are mistakes that I see all the time.
 
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Thank you, Fact Checker.
Besides the assumptions statement. Is my solution correct?
 

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