A random variable x has a mean of 22 and a standard deviation of 3.1. Random samples of size 40 are drawn, and the sample mean calculated each time. What is the probability that, for a given sample, is 21?

Respuesta :

in this question, we are given the poverty function Our X equals no point to for X equals not 123 on before. So we are asked to find the mean and standard deviation. So the first step is to dio our property distribution tables. We are no one to hey wonderful. When we get told, it's no point to went to Teoh went to and not point to stuff. It's nice and easy. The next room we need to do is X he exit. We're gonna times are probability of X which is not 20 for all of them and by the value of X itself. So for the 1st 1 we're times in nor point to buy zero So we get zero 2nd 1 time to North point to buy one which is no point to no no point to about two, which is full no point you by three which is six and no 60.2 times four which is ain't on Then the way we get the main is to some all these together. So every animal together we get to not to is me which is on me I'm just gonna put less some of X P x is a reminder of how we got that. So if we do total so the next thing we need to dio is doomed. Ex spread P X so x zero squared is still zero and zero times. Anything is zero once where it is still one so that times not point to a store not point to. But now two squared is four of four times no point to there's no 0.8 three squared is nine. So no 90.2 times nine is now. One point ain't on four spread is 16 so one out of the North Point to buy 16 which is 3.2 on the total for that is not quick to note. 0.8 plus 1.8 plus 3.2, which gives us six. So we now need ah variation, which is the expectation of X. It's what, which is this Butthead and we need to take from that expectation of X, which is our mean squared same. We're looking at six minus to squared. So that's six minus four, which is to on to get the standard deviation. We just need to do root off answer. So If we do, son deviation equal root of Arians equals route to Ruutu is actually an irrational number. So it will just keep going forever. So we'll just simplify to one distal place, which is 1.4. So they haven't you mean is too on the standard deviation is 1.4.