idiotbrothers – Hearseeno

idiotbrothers:

hearseeno:

…deleted lots of boring stuff about statistics….

THANK YOU SO MUCH. Not quite the way my professor taught it, but it makes a lot of sense laid out like this! If you want me to write you a ficlet or something in return, feel free to shoot me an ask :’)))

You’re welcome. I’m kinda boggling at the fact that they’re still making people convert from percentiles to z scores using that dratted table. I remember first learning to use it back in 1984.

If you feel like you owe me anything, you could keep an eye out for my SPN Reverse Bang art submission come the new year. If I know at least one person will comment on it, then I can reassure myself that I’m not putting all this effort into something that will only get flung out into the vast dark void that is the internet never to be heard of again. 😛

THE TABLE IS CRUEL AND UNUSUAL

and yeah, of course!! Are you gonna be posting it to LJ w/ this same username? I’m actually participating in Reverse Bang, too, but as a writer, so u never know~

Yep, posting under the same name on LJ, but I’ll probably post a bit of a project diary on this tumblr once they do the reveals. lol, yes, and you never know…

…deleted lots of boring stuff about statistics….

THANK YOU SO MUCH. Not quite the way my professor taught it, but it makes a lot of sense laid out like this! If you want me to write you a ficlet or something in return, feel free to shoot me an ask :’)))

You’re welcome. I’m kinda boggling at the fact that they’re still making people convert from percentiles to z scores using that dratted table. I remember first learning to use it back in 1984.

If you feel like you owe me anything, you could keep an eye out for my SPN Reverse Bang art submission come the new year. If I know at least one person will comment on it, then I can reassure myself that I’m not putting all this effort into something that will only get flung out into the vast dark void that is the internet never to be heard of again. 😛

idiotbrothers:

hearseeno replied to your post: does anyone know how to work w/ z-scor…

maybe…depends on what you’re trying to do with them.. Taught psych stats at one point in my career. Let’s see if I remember the basics. 😛

crosses fingers that u still remember

I’m supposed to be doing a bunch of different crap with them, but here’s a sample problem: “A set of scores has a mean of 16 and a standard deviation of 3. What score separates the top 30 percent of the population from the lower 70 percent?”

The formula we were given for this set of problems was the one that goes, (‘score of observations’ minus ‘mean’) divided by (‘standard deviation’)

i cant for the life of me figure out if i’m plugging everything in correctly, and after, how to be sure if I’m selecting the right proportions from the z-score table

Okay, that’ll take a couple steps. You’re looking at the table in your book of z score associated with proportions of area under the standard curve, yeah?

So, what you’re looking for is the z associated with the 70th percentile:

Remember that right smack dab in the middle of the perfectly balanced normal curve is the 50th percentile. In order to get to the 70th percentile using the wacky table they provide you, you’re going to need to look for the 50th + xth = 70 – so, you’re looking for 20 percentage points above the mean.

So, looking at that table for as close to .20 (20%) as I can get for that purple section, it looks like that’s associated with a z of 0.53. Is that what you get? Are they telling you to take the closest? Round up? down?

Now that you have a z score, you need to use your formula to convert the z score into the observed score scale.

z = (ObservedScaleScore – ObservedScaleMean) / ObservedScaleStandardDeviation

0.53 = (x-16)/3