statistics question

[cookderosa]

Ok, I think I am starting to get into my statistics groove, but then I just got stumped on a few practice questions tonight. In my practice questions, they ask for the standard deviation. My calculator (and book) use n for "population SD" and n-1 for "sample SD"....so in the question, what would be my assumption if they don't specify population or sample? Their answer matches population, so I see what they did, but will the DSST exam specify which they want, use or is there a rule of thumb?

THANKS!!!

[gus]

I've taken this exam last month and I don't believe there was any confusion about this, it will be clear in the question whether it's a sample or a population.

[cookderosa]

Originally Posted by gus

I've taken this exam last month and I don't believe there was any confusion about this, it will be clear in the question whether it's a sample or a population.

>>


Ok Gus, thanks, that's very helpful!!

[jec959]

Jennifer how are you doing keeping the formulas straight I feel like I have to many of them kicking around my brain. Oh yeah according to the ic flash cards you can't tell if its a population or a sample until you see the question ask, so apparently its a population. What are you using for sample tests?

[cookderosa]

Originally Posted by jec959

Jennifer how are you doing keeping the formulas straight I feel like I have to many of them kicking around my brain. Oh yeah according to the ic flash cards you can't tell if its a population or a sample until you see the question ask, so apparently its a population. What are you using for sample tests?

Judy,

Ok- well, first, I am blissfully unaware of all that I don't yet know- so don't tell me anything hard. So far I'm treading water.

Seriously.

I am first studying through the Standard Deviants series, I am on disk 4. As I go, I read the appropriate Idiot's Guide chapters (up to chapter 5). Simultaneously, we are watching the Against All Odds (Teacher Professional Development and Teacher Resources by Annenberg Media) videos, but they are not fitting neatly into my plan- I can't make an obvious connection about which ones fit where...but we are getting there. We are on program 6 with them.
I do the practice problems as they are presented. I am doing this with my 13 year old son, so we are going kinda slow, but I'm not complaining! It's going very well. I also own, but have not yet used, the Dummies Workbook and a college textbook with solutions if necessary.

Last night, I spent around 4 hours playing with and learning how to use my calculator. (which ISN'T taught in the directions- what's wrong with people?) Now, I'm going to look really dumb here, but this is my first scientific calculator ever (I didn't even take algebra in high school)- and WOW it does COOL stuff!?!? I HAD NO IDEA a calculator would follow order of operations for you!! (shhhh....I didn't tell this to my son, he needs to learn this for his math class) I also had no idea a calculator would find the square root, mean, and standard deviation FOR YOU!? Simply a button! Wow! So, anyway, this would have been nice to know last week when my son and I worked about 20 SD population and SD sample problems long hand. But, hey, there is something to be said for learning, and if nothing else, I CAN do a standard deviation like nobody's business. (I really thought I would have to work them out long hand on the test!) I only know a few symbols, and a few formulas, but I imagine my calculator can do a lot more. It's nerdy, but very exciting! (we both have the TI 36x solar)

So, to answer your questions, I think you are probably a lot farther along than I am in the material. We are just now starting probability, and my IC subscription is expired, so I won't be using the flash cards for this one. I googled "probability questions" and found a page for gifted 6th graders which had a few practice problems and a little tutorial. I managed to get them right (yeah), but when I looked ahead in the website, my eyes rolled back in my head- so I am just going to keep going one bite at a time.

I am sure there are lots of little 6th graders who can tell me the probability of students who has a green shirt and a red shirt and a yellow shirt, but only half of his friends have a purple shirt which has a yellow stripe except for the ones with a blue stripe, but they only wear white shirts on Sunday and that's when their mom does laundry on Friday, so which shirt are they more likely to wear on an odd day of the week if their mother doesn't do laundry until Sunday? Uhhhh yeah, I'm not there yet!!

[barcotta]

My two cents--

For Statistics, I would be careful about using too many different sources. I lost a lot of time trying to match things up and it all can become unnecessarily confusing. If I had it to do again, I would use the Standard Deviants videos, one book (one of the books that those who have gone before us were successful with) and the Berkeley podcasts for probability (which it sounds like you may be already past, but I needed them). Annenberg (sp.) had way too much fluff and was a waste of time. Also, random internet research, which served me well on most everything else, almost made me insane for this exam. I'm sure you and your son will do well no matter what method you use--but if you take my suggestion it should at least save you a little time and frustration. Good luck!

[jec959]

I believe Barcotta may be right and I have been using to many books, I have started just using the idiots guide to statistics although I did read through statistics demystified completely as well, part of my confusion seems to be that different books use different methods. I started using just the one book late last week. I need to practice with my calculator more as well. I have been doing standard deviations by hand although I have been doing permutations and combinations on the calculator.

[gus]

If I remember well, the idiot's workbook had a good section on null hypothesis with just enough information.

I did jump to several sources while preparing for this one, and I think I agree with Barcotta, it was a bit confusing at times (I had IC, Annenberg videos, the Demystified book-didn't read it, the idiot's workbook-skimmed through, Statistics in plain English book and some internet research).

One of the reasons this was somewhat counterproductive was the many different notations and representations of formulas used. The Annenberg videos were too fluffy for my taste as well (although I was watching them at 1.8-2x the normal speed, it was still boring at times), I believe I only winded up watching 7 videos (attempted 2 more of the ones towards the end just to see where it was going but decided to stick with books).

It's amazing that your 13 year old son is assimilating the material, he must be well ahead of his age, isn't he?! I wouldn't complain either, no matter how slow it gets, I'd surely do whatever takes if my son shows interest at such an age, you must be very proud of him.

Best of luck!

[cookderosa]

You guys are awesome. Ahhhhh....a reason to dump the annenberg videos....SOLD! Those suckers are out. They are too fluffy- maybe that's why I can't match them nicely. (which drives my type A, OCD self nutty)

Yes, I am going slow- I have until the end of May before I have to test. My son doesn't "have to" test ever, so if it gets too hard for him- so be it. As for now, he is doing fine. The problem for him is simply that everything is new- he had never heard the word "mean" or even concepts like "negative correlation" and "population" all have to be learned- where an adult has probably at least heard of them. I don't know if I said it here or on another board- but I offered him $100 if he passes. I never tell him to study, it's no pressure- totally up to him. So far, he hasn't missed joining me for one of "my" study sessions yet! I don't know if he will do it or not, BUT I never think learning is wasted!!! (test or no test). I did promise him that I wouldn't let him go in there if I didn't think he had a chance of passing - and that I'll stick to. I also told him that if he passes it now or in 10 years- that my offer for a hundred bucks is still good. My only rule, is that he can't study during school (lol that sounds funny) but I told him this was a fun extra thing he gets to do (lol now that REALLY sound funny) but that it had to be on his own time. And yes, I am very proud of him. He is bright- and I have no doubt he could get through this either this or next year.

I am going to slim down my resource list, and stick to my Idiot's guide along with my SD videos. Thanks!!!!