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Get to know PDF st095 L6

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    We can do the same with normal distributions. Which are modeled by a special
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    probability density function. We're not going to go over the equation for this
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    probability function in this course, but if you want, you can easily look it up
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    and see what it is. And that might be pretty cool for some of you that wants a
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    little bit more information. But basically, since we have this theoretical
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    curve, we can model it with an equation. And then, using this equation, we can
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    use calculus to find the area under the curve. But we don't need to use
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    calculus, because someone else already did, and then they created a special
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    table so that we can always figure out the area under the curve between any two
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    values. We're going to use this table later first let's make sure we're all up
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    to speed on the normal probablity density function and the area underneath.
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    First the tails never actually touch the X axis they get closer and closer to
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    the X axis so the X axis a horizontal axis. [unknown] the reason the tails of
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    this theoretical model don't touch the x axis is basically because we can never
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    be 100% sure of anything, in other words we could have a value way out here
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    really far from the mean like five standard deviations away But the probability
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    of getting this value or lower is very small. And it's equal to the area under
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    the curve. So if we could zoom in, we would see this tail get closer and closer
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    to the x axis but never touching And then the area in between the tail and the x
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    axis all the way to negative infinte is the probability of getting this value or
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    lower. We'll go more into depth in that in a second. And similary we could get a
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    value way out here But the probability is very small so basically what you have
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    to remember is that if we have certain value let's just call it X for now that
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    the area under the curve from negative infinity to X is equal to the probably of
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    randomly selecting a subject in our sample less than X and this equal the
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    proportion in the sample of population. With scores less than x. If this is a
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    little confusing, don't worry. That's the whole point of this lesson. You're
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    going to get really comfortable with using the probability density functions and
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    analyzing this area, and finding this area.
Tytuł:
Get to know PDF st095 L6
Video Language:
English
Team:
Udacity
Projekt:
ST095- Statistics
Duration:
02:36
Cogi-Admin added a translation

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