The cumulative distribution function cdf of the standard normal distribution, usually denoted with the capital. Capitulo juan aller gustavo pages contraccion uterina y. In probability theory, a normal or gaussian or gauss or laplacegauss distribution is a type of continuous probability distribution for a realvalued random variable. A random variable, usually denoted as x, is a variable whose values are numerical outcomes of some. As cdfs are simpler to comprehend for both discrete and continuous random variables than pdfs, we will first explain cdfs. The parameter is the mean or expectation of the distribution and also its median and mode. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Scribd is the worlds largest social reading and publishing site. This tutorial provides a simple explanation of the difference between a pdf probability density function and a cdf cumulative density function in statistics. Random variables, pdfs, and cdfs university of utah. An intuitive way to see that a holds is the following. Pregnancy age ranged from 27 to 39 weeks, with a mean and standard deviation of 33. Before we can define a pdf or a cdf, we first need to understand random variables. The normal cumulative distribution function cdf is.