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Results for distribution cdf pdf cumulative
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113 votes
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Consider the sum of $n$ uniform distributions on $[0,1]$, or $Z_n$. Why does the cusp in the...

From this it is immediate that the cumulative distribution function (CDF) is $$F_X(x) = \Pr(X \le x) = |(-\infty, x] \cap [0,1]| = |[0,\min(x,1)]| = \begin{array}{ll} \left\{ \begin{array}{ll} 0 & … Because the PDF is the derivative of the CDF, this implies that each time we add an independent uniform variable to $Y$, the resulting PDF is one time more differentiable than before. …
whuber's user avatar
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89 votes

Central limit theorem for sample medians

The middle plot is the cumulative distribution function for the same distribution: it uses height to denote probability. It shares its horizontal axis with the first plot. … Let $F$ be the CDF of the original distribution (middle plot) and $G$ the CDF of the Beta distribution. …
whuber's user avatar
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81 votes
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Are CDFs more fundamental than PDFs?

Every probability distribution on (a subset of) $\mathbb R^n$ has a cumulative distribution function, and it uniquely defines the distribution. … The simplest example of a distribution lacking a PDF is any discrete probability distribution, such as the distribution of a random variable that only takes integer values. …
Ilmari Karonen's user avatar
54 votes
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Why is the sum of two random variables a convolution?

In terms of (cumulative) distribution functions (cdf), it is an operation closely related to the convolution. (See the references.) … The first two of these are special insofar as the box might not have a pmf, pdf, or mgf, but it always has a cdf, cf, and cgf. …
whuber's user avatar
  • 334k
51 votes
3 answers
8k views

Are CDFs more fundamental than PDFs?

My stat prof basically said, if given one of the following three, you can find the other two: Cumulative distribution function Moment Generating Function Probability Density Function But my econometrics … How do I know whether a PDF or a MGF can be derived from a CDF? …
Stan Shunpike's user avatar
45 votes
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Simulating draws from a Uniform Distribution using draws from a Normal Distribution

Suppose the target distribution has PDF $f$. A value $Y$ is drawn according to another distribution with PDF $g$. … We can accomplish this by fitting the largest possible rectangle (representing a uniform distribution) beneath a Normal PDF. …
whuber's user avatar
  • 334k
29 votes

Weibull distribution parameters $k$ and $c$ for wind speed data

ldots,f_{n}$ and cumulative frequencies $p_{1}=f_{1}, p_{2}=f_{1}+f_{2}, \ldots, p_{n}=p_{n-1}+f_{n}$, then you can fit a linear regression of the form $y=a+bx$ to the values $$ x_{i} = \ln(V_{i}) $$ $ … Using bootstrap to add pointwise confidence intervals to the PDF or CDF We can use a the non-parametric bootstrap to construct pointwise confidence intervals around the PDF and CDF of the estimated Weibull …
COOLSerdash's user avatar
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27 votes
3 answers
112k views

Finding the PDF given the CDF

How can I find the PDF (probability density function) of a distribution given the CDF (cumulative distribution function)? …
Mehper C. Palavuzlar's user avatar
22 votes
1 answer
5k views

At What Level is a $\chi^2$ test Mathematically Identical to a $z$-test of Proportions?

Equating this to the $pdf$ of the normal (now the $x$ in the $pdf$ will be $\sqrt{y}$ to be plugged into the $e^{-\frac{x^2}{2}}$ part of the normal $pdf$); and remembering to in include $\frac{1}{\sqrt … This formula seems to rely on the binomial distribution. …
Antoni Parellada's user avatar
21 votes

What does " Y axis" mean in continuous probability distribution?

There are two common ways to represent a probability distribution, the probability density function (PDF) and cumulative distribution function (CDF). I suspect you're wondering most about the former. … For the latter, the distribution is plotted as cumulative from zero to one, so the y-axis is the sum of the distribution up to a given value of x. …
Bryan Krause's user avatar
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20 votes
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What's the distribution of $(a-d)^2+4bc$, where $a,b,c,d$ are uniform distributions?

Often it helps to use cumulative distribution functions. … Writing $x=(a-d)^2$ with CDF $F$ and $y=4 b c$ with PDF $g = G^\prime$, we need to compute $$H(\delta) = \Pr((a-d)^2 + 4 b c \le \delta) = \Pr(x\le \delta-y) = \int_0^4 F(\delta-y)g(y)dy.$$ We can expect …
whuber's user avatar
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17 votes
6 answers
5k views

Probability theory books for self-study

Are there any good books that explain important concepts of probability theory like probability distribution functions and cumulative distribution functions? …
16 votes
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Distribution of sum of exponentials

Start with the cumulative distribution function (CDF) for $S_2$. … Again, start with the cumulative distribution function (CDF) for $S_2$. …
SecretAgentMan's user avatar
14 votes

Distribution function terminology (PDF, CDF, PMF, etc.)

Cumulative distribution function (CDF) is sometimes shortened as "distribution function", it's $$ F(x) = \Pr(X \le x) $$ the definition is the same for both discrete and continuous random variables. … Probability density function (PDF) is a continuous equivalent of discrete probability mass function (PMF). …
Tim's user avatar
  • 141k
14 votes
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What does Φ mean?

The Phyrexian or Greek letter Φ is being used to describe the CDF (cumulative distribution function) of the standard normal. … The lowercase Greek letter φ is being used to describe the PDF (probability density function) of the standard normal distribution. …
Sextus Empiricus's user avatar

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