# Statistics with Probability

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• Probability
• #12612

Please discuss concepts and examples from probability as well as reviews of websites you have found interesting.

#15036

I looked at the site many-eyes.com, that site has alot of useful information about graphs and charts that we can create to show how our datas compare to one another. From the looks of it, it seems a bar graph is the best way to go. Mutually exclusive means that there are two events but both cannot occur at the same time and conditional means that two events can occur at the same time? Or that an event can occur even if one has already occurred? Just curious.

Chandini P.

#15037

Yes, mutually exclusive means that there are two events but both cannot occur at the same time. From the point of set theory, each event is represented by a set of outcomes. If the events are mutually exclusive, then their intersection is empty.

Conditional means that you restrict the set of outcomes under consideration to one event (the given) and then look at another event. In January, P(snows | precipitates) is going to be higher than P(snows), since we are looking at a more restrictive set (precipitates) but which contains the other set (snows). On the other hand P(clear skies | precipitates) is going to be smaller than P(clear skies). In fact the events “precipitates” and “clear skies” are mutually exclusive.

One word of caution regarding your last question, is that you should not think of events as necessarily happening in real time. Instead, it is better to look at the subject from the point of view of sets. However, if an experiment has finished and an outcome has been determined, then that’s it, no new events can occur.

#15042

Thank you for explaining that. Since the intersection is empty, then A is shaded and B is shaded but nothing is common (that’s how I will get the concept, lol). OK, so because there’s clear skies that doesn’t mean it will precipitate. Also, on one of the questions about taking out a ball from an urn and then taking out a second ball, without replacing. So say there are 10 balls, and you take the first one so it’s 1/10. Then you take a second so 2/9? Or would it be 1/9 and 2/8? Because you are taking out a ball so that leaves 9 and then you are taking a second but you’re not putting in the first one therefore only 8 balls are left. Am I getting the right concept here?

#15097

as i prepared for class today, i accidentally also read section 5.6, hypergeometic random variables. why was the section skipped over? not a useful random variable to understand?

#15100

why is the constant e used to compute poisson random variables and not some other constant?

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