Basic Statistics Problem?

Question

For the life of me I can't remember how to do this kind of problem. I know it's really basic, I just can't remember the formula.

This isn't the homework problem, this is a generic version - I need the formulas.

Given a sample of mean u, variance o^2 and sample size n, what is the probability that | u - X | <= d.

I know the formula is P( |N(0,o^2/n)| <= d) = p, but I don't really know how to solve that. I don't really even know what it means, actually.

I also need to know how to work backwards with p given and finding d.

Once again to point out, this ISN'T the actual homework problem, so a complete answer would be nice.

Answer 1

I'll try to help, but I'm not entirely sure what you need.

You need the standard deviation which is the square root of the variance. You might be needing the z score formula which is (number - mean)/standard deviation
or
(xbar-mu)/sigma

Once you have the z score you can look in the z score table to find your probability. For example, if your z score is 1.23, the area to the left is .8907 which is your probability.

I hope this was helpful.

Answer 2

Set y = 0 for the two equations. Mark a dot at that factor on the x axis. a) 0 = 2x+a million : x = -a million/2 b) 0 = a million/2 x + 2 : x = -4 Set x = 0 for the two equations. Mark a dot at that factor on the y axis. a) y = 0 + a million : y = a million b) y = 0 + 2 : y = 2 connect the two dots you made for each equation, you ought to get 2 lines. expand those lines to make your graph.