Tuesday, December 7, 2010

What I'm up to...

SO Angela is Tiny Tuesday'ing away....
Amanda is enjoying some tea and trying to make the best of her weather...
Jill is working on a spectacular Radiating Star quilt for granny

Me?.....

I'm TRYING not to feel dumb....

I just taught myself a lesson on Confidence Intervals....


ie: If I take a sample (n=1077) of young women whose mean quantitative score (x-bar) is 275 on a national NAEP test and knowing the population standard deviation (sigma) = 60....

A 95% confidence interval has me using a critical value (z*) of 1.96 and sample mean standard deviation of 60/squ rt(1077)
Therefore, I can be 95% confident that the true population parameter (the population mean) is between:

275 +- 1.96(60/sqr rt (1077))
which equates to :
271.4166 to 278.5834

and that my margin of error is 1.96(60/squ rt (1077) = 3.5834


In layman's terms

If I were bored and went out asking 1077 young ladies how they scored on their NAEP tests, I can, with 95% confidence say that, the average score of the 1077 ladies will fall between 271.4166 and 278.5834. OR that the average will be 275 +- 3.5834 points.




{{{{I think}}}}

5 comments:

Jackie said...

You're confidence interval reminds me of Six Sigma. Other than that, it's too late and my brain is too fried to think further. I don't know how you do this after a long day!

scraphappy said...

Don't you just love bell curves? My kids are always begging me to curve their tests, then I try to explain to them what a curve really is. I don't think they get it though. Try not to fry your brain. AP classes go down much smoother the second time through. By year three it might even be fun.

Amanda said...

Now that I'm retired I'm trying to keep my brain active, but prefer to do it via sudoku and other puzzles, or Brain Training on my Nintendo DS; so I'm not even going to try to make sense of your puzzle! It reminds me too much of when I was teaching and having to make sense of Value Added graphs, and SAT result graphs, and gender result graphs, etc etc.

Patchwork Penguin said...

Thank you for reminding me why I am not a math teacher.... can you translate all of that into English please??? ;O)

Lori said...

a bell curve?? LOL--I'm not into math--but I understand the diagrams!