the odds of seeing visitors on given dayit turns outcomes out to about or probability very interesting alrightso those are some common data distributions you might run into in the real world remember we used probability distribution function with continuous databut when we're dealing with discrete datawe use probability mass function so that' probability density functionsand probability mass functions basicallya way to visualize and measure the actual chance of given range of values occurring in dataset very important information and very important thing to understand we're going to keep using that concept over and over again alrightlet' move on percentiles and moments nextwe'll talk about percentiles and moments you hear about percentiles in the news all the time people that are in the top of incomethat' an example of percentile we'll explain that and have some examples thenwe'll talk about momentsa very fancy mathematical conceptbut it turns out it' very simple to understand conceptually let' dive in and talk about percentiles and momentsa couple of pretty basic concepts in statisticsbut againwe're working our way up to the hard stuffso bear with me as we go through some of this review percentiles let' see what percentiles mean basicallyif you were to sort all of the data in dataseta given percentile is the point at which that percent of the data is less than the point you're at common example you see talked about lotis income distribution when we talk about the th percentileor the one-percentersimagine that you were to take all the incomes of everybody in the countryin this case the united statesand sort them by income the th percentile will be the income amount at which of the rest of the country was making less than that amount it' very easy way to comprehend it in dataseta percentile is the point at which xof the values are less than the value at that point