pi capital n Sigma squared Rho beta 1 beta 0 those are all parameters ok the statistics x-bar s and P hat s squared R b1 and b0 are all statistics so there's going to be some problems in in my book that I have my classes do that just get used to writing the letter so I'm getting used to figuring out you usually you'll have a computer program that will say you know P equals blank and P hat equals blank or or mu equals blank and X bar equals blank right so you have to sort of get used to what do these letters actually represent and be able to sort of plug in a number into a computer program so if it's going to do some advanced calculations for you you have to be able to sort of know what letter goes with what so here's a good example a lot of times you'll read an article or something like this especially when we get to hypothesis test you'll see this all the time where you have somebody has said something about populations but then they're using sample data to figure out if that population guesses right so if you look at this example it says IQ tests are supposed to be to have a population mean of 100 and a population standard deviation of 15 but at a random sample of 45 adults found that the sample mean was ninety seven point seven and the sample standard deviation was fifteen point three so if you see in this problem we actually have five numbers that are listed in this paragraph and what our goal is to see which let which of these letters we've done goes with which number and tell me if it's a sample statistic or it is a population parameter all right so it's just getting used to reading stuff and being able to sort of pick out the information you need so notice it said that the IQ tests are supposed to have a population mean of a hundred and population standard deviation of 15 they did say population here right so this is not a sample mean this is a guess about everybody that's ever taken an IQ test so the population mean well that's the Greek letter mu so if I was doing this in a computer program all right right mu equals 100 and that would be a parameter right since it was a it was a guess about the population and the population standard deviation we said was the Greek letter Sigma so Sigma is 15 and that's also a parameter but now they said they took a random sample of 45 adults so 45 adults that's the number of people in your sample data or the number yes so this is notice that's gonna be sample size right how many people are objects or in your in your data is that called the sample size or sample frequency so that's the lowercase n so lowercase n is going to be 45 and that was a statistic the sample mean what's the letter for sample mean x-bar so x-bar is ninety seven point seven that's also a statistic it came from sample data and sample standard deviation that's our our letter s so that was 15.3 and again we're gonna write statistic next to that just to get into you hope just to know which one it was sample data and which one was the population again a lot of times in computer programs you'll see mu equals blank Sigma equals blank x-bar equals blank s equals blank you've got to be able to type read something like this and be able to type it in to the computer program okay so you just want to be kind of aware what these letters are representing let's look at another one very common one voting so they're trying to see who have what percentage of people are going to vote for a candidate especially when they're political elections come up we're always looking at that so they took a poll of 200 people and they found that forty seven point two percent of people in the poll voted for plan on voting for the candidate the actual votes on voting day though was forty one point three percent so notice first of all we have two engines remember there's only really letters here that represent percentages is either P hat or PI or P notice again population percentage proportion would be pi and sample proportion would be P hat so it's just a matter of kind of thinking about what's the population and what's the sample well notice a poll is not everybody right that's not all the all of millions of people that vote this is this is just a poll of 200 people that has to be a sample that's not everybody in the whole voting population so the 200 was really our sample size so again N equals 200 that's nurse Moll letter n so that was a statistic and that means that percentage that they calculated from that poll is really just a sample percentage but remember in the computer programs if it says P hat equals you can't leave it as a percentage you have to convert it back to a proportion so in our case we're going to write 0.47 - and all I'm doing is dividing by a hundred with the decimal two places to the left that's what I would type in the computer and again that's also a statistic it came from sample data now on the actual voting day when millions of people voted there was 40 1.3 percent voted for the candidate so that's the actual population percentage so that's our population proportion for voters so you could actually use one of two letters you could write it as pi equals zero point four one three or you could write it as P equals zero point four one three either way those would be a parameter estimate we're trying to have that was the actual population percentage of population proportion I tend to use pi the Greek letter pi but some some depends on your stat teach or some stat teachers you prefer P I would say more stat teachers use P than PI I'm kind of old school okay so this we're gonna be doing some of my students are going to be doing some problems like this and just practicing learning their letters so it's really good to sort of start to kind of learn these letters as we go through the class I'll always be reviewing these letters as we need them as we see a new formula or something like that but it's a good this is a good introduction to warm up to all the letters we see in stats alright so I hope this was helpful this is Matt Chi's show and intro stats and I'll see you next time