DSST Statistics, standard deviation

[themaboys]

Hi guys,

My name is Tim and I am studying for DSST Principles of Statistics.
I cannot figure out why some places list the formula for standard deviation as "the square root of the sum of (x-mean)^2 divided by (n-1)" and other sites say the formula is "the square root of the sum of (x-mean)^2 divided by (n)"

What does the (n-1) or just plain (n) do in the equation?

Thanks,
Tim

[kimaya24]

Hey Tim, I just passed statistics a couple days ago and I celebrated all weekend!!

To answer your question, when it says n it's for a population, n-1 is for a sample. This one threw me off too, here's a link to some videos that really helped me understand this better, the first few videos go over standard deviation.
Khan Academy

[themaboys]

Hey Tim, I just passed statistics a couple days ago and I celebrated all weekend!!

To answer your question, when it says n it's for a population, n-1 is for a sample. This one threw me off too, here's a link to some videos that really helped me understand this better, the first few videos go over standard deviation.
Khan Academy

Thank you very much! I understand now!
I will definitely check out that Khan Academy site too..

By the way, do you have any advice/input/comments regarding the Statistics DSST?
I don't really know what to expect..


Thanks again!
-Tim

[clep3705]

You will not compute the standard deviation from raw data points as you must to complete the IC flashcards. Instead, you'll be given the intermediate values. This is true for all formulas. When you look at the various parts of statistical formulas, they have specific names. Names such as sum of the x's, sum of the squares of the differences, etc. That's what you're given. I'll use a capital E instead of the Greek symbol sigma. Expect to be given something like:

Ex
Ey
Exy
E(x-mean)squared

You'll have to take those values, plug them into a formula, and compute the result. I didn't expect that, which is why I missed a few. I wasted my time learning how to enter raw data points into my TI-30X II S calculator. If I had memorized the formulas instead, I might have made a perfect score.

When you look at the answers on the flashcards, memorize the formulas you see there.

[themaboys]

Do you guys know of any other special topics/formulas I should know for DSST Statistics?

Thanks for all your guys help!
Tim

[eprush21]

I'm getting ready to take the test in about 2 weeks. Other then IC, do you have any other recommendations??? I have never studied Statistics, so I don't really know what to do/expect. Thanks for all your help!

[Excelmywayup]

When you do take the DSST Statistics exam, please come back to this thread and post how you did. I have never studied stats either and would like to know how hard it was / if you passed. Thanks man and good luck!

[ryoder]

Just a reminder that you guys can take ALEKS -- Assessment and Learning, K-12, Higher Education, Automated Tutor, Math statistics for $20 per month. You can use aleks as a learning tool and take THE DSST test for $80 or you can use ALEKs to get ACE credit for statistics once you assess at 70%. I did this in 1 week of intense studying over 2 weekends.

The ALEKs credit works at TESC and Exelsior for sure and you can actually grab about 12 credits in math for transfer to TESC for your 20 dollars.

[sarahw1357]

I took the Stats DSST exam, the paper version, a few weeks ago. I would definately know standard deviation, how z-scores and t-scores work, and correlation and regression stuff well. I was suprised to find not many problems involving probability but maybe there is a difference between the computer and paper versions because from what I read on this forum I thought there would be a lot. There were a few random questions on ANOVA which I just guessed on and a few questions that I had no idea what was going on. Probably a fourth of the questions and maybe even more were gimmies like finding the mean, range, mode, etc... I studied IC flashcards and went through the whole complete idiot's guide to stats second edition before taking this exam. I found it to be challenging and I still haven't found out my score so I'm a bit nervous but I think I passed. A few equations I remember using are standard deviation, standard error, lots of z-score calculations, finding the sample size,and there are a few others that I can't remember right now. If you know the concepts on IC and the main formulas very well I think you should do fine. There will be questions you have no idea on but don't let that get you down.