Post by: vexx on December 12, 2009, 10:54:12 pm
Approx 8-9% get above 40 in the subject, and 2% get above 45.
But what percent gets 41, 42, 43, 44, 46, 47, 48 and 49?
Thanks:)
Post by: Cataclysmic on December 12, 2009, 10:55:30 pm
Post by: kyzoo on December 12, 2009, 10:56:24 pm
Post by: vexx on December 12, 2009, 10:57:00 pm
It's 8-9% of people get above 40 and 2% of people get above 45.
oops i meant that .__.
lol u can work it out if you done methods
errrr, is it bad that i'm not sure .:P
Post by: kyzoo on December 12, 2009, 11:00:09 pm
Post by: vexx on December 12, 2009, 11:01:20 pm
lol no u haven't done methods so :Poh haha i thought you meant 1/2.
well you've done methods?
who is man enough to take on this intense & hard mathematical problem? :P
Post by: Gloamglozer on December 12, 2009, 11:17:47 pm
lol no u haven't done methods so :Poh haha i thought you meant 1/2.
well you've done methods?
who is man enough to take on this intense & hard mathematical problem? :P
Where is TT when you need him? :P
I remember what a z-score was though lolz
Post by: crappy on December 12, 2009, 11:19:53 pm
and SD=7 ( ithink)
and use normalcdf. done
Post by: Gloamglozer on December 12, 2009, 11:25:00 pm
let u=30
and SD=7 ( ithink)
and use normalcdf. done
Yeah, sd is 7.
Post by: vexx on December 12, 2009, 11:25:46 pm
Post by: bloodboy on December 12, 2009, 11:28:30 pm
Post by: Gloamglozer on December 12, 2009, 11:28:37 pm
^oo sweet where abouts is normalcdf on the TI-89?
You'll have to go into Stats/List and then press F5.
EDIT: Or you can do the above. Like the god says, "Whatever floats your boat."
Post by: crappy on December 12, 2009, 11:29:20 pm
EDIT: Beaten by Gloamy hahaha
Post by: vexx on December 12, 2009, 11:29:37 pm
is this 1 and 30?
Post by: crappy on December 12, 2009, 11:30:24 pm
^ noob question, what do i put for lower value and upper value?
is this 1 and 30?
thats the range you want, so if you want to find the % of ss above 40, put lower bound as 40 and upperbound as 50
Post by: Gloamglozer on December 12, 2009, 11:31:18 pm
^ noob question, what do i put for lower value and upper value?
is this 1 and 30?
thats the range you want, so if you want to find the % of ss above 40, put lower bound as 40 and upperbound as 50
And then "Bob's your uncle". It's around 8%.
Post by: crappy on December 12, 2009, 11:32:34 pm
^ noob question, what do i put for lower value and upper value?
is this 1 and 30?
thats the range you want, so if you want to find the % of ss above 40, put lower bound as 40 and upperbound as 50
And then "Bob's your uncle". It's around 8%.
or, you could say "Robert is your mother's brother", haha lame joke from some movie
Post by: vexx on December 12, 2009, 11:32:39 pm
in normal cdf, i put in
40
50
30
7
and it comes up with cdf=0.074426
whats happening o_o
Post by: crappy on December 12, 2009, 11:33:36 pm
Post by: vexx on December 12, 2009, 11:34:59 pm
Post by: stonecold on December 12, 2009, 11:51:18 pm
Edit: That should have read 0.1%. Bit late to be doing maths lol.
Post by: crappy on December 12, 2009, 11:54:16 pm
WTF! It is saying that less than 0.01% get a 50. :(
Post by: stonecold on December 12, 2009, 11:59:08 pm
Post by: crappy on December 13, 2009, 12:01:25 am
what did you put in the calc?
Post by: m@tty on December 13, 2009, 12:03:00 am
Post by: QuantumJG on December 13, 2009, 12:03:57 am
let u=30
and SD=7 ( ithink)
and use normalcdf. done
I prefer probability cheat.
Post by: crappy on December 13, 2009, 12:05:09 am
let u=30
and SD=7 ( ithink)
and use normalcdf. done
I prefer probability cheat.
no way, the ti 89 cas absolutely rapes ti 83/84
Post by: Gloamglozer on December 13, 2009, 12:09:07 am
let u=30
and SD=7 ( ithink)
and use normalcdf. done
I prefer probability cheat.
no way, the ti 89 cas absolutely rapes ti 83/84
+1 We've got "F2 Solve". :P
Post by: stonecold on December 13, 2009, 12:11:16 am
Then I did what m@tty suggested and went:
normCDF(49.5,50,30,7) and got 0.000533 which is 0.05% :o
This is confusing LOL. And TI-Nspire rapes them all! ;D
Post by: Gloamglozer on December 13, 2009, 12:12:28 am
First I did normPDF(50,30,7) and got 0.000962 which is 0.1%
Then I did what m@tty suggested and went:
normCDF(49.5,50,30,7) and got 0.000533 which is 0.05% :o
This is confusing LOL. And TI-Nspire rapes them all! ;D
You can't use normPDF... You must use CDF for all.
And also, The TI-nspire has too many buttons and it's too chunky to carry around.
Post by: crappy on December 13, 2009, 12:12:47 am
Post by: stonecold on December 13, 2009, 12:16:54 am
Post by: m@tty on December 13, 2009, 12:17:12 am
First I did normPDF(50,30,7) and got 0.000962 which is 0.1%
Then I did what m@tty suggested and went:
normCDF(49.5,50,30,7) and got 0.000533 which is 0.05% :o
This is confusing LOL. And TI-Nspire rapes them all! ;D
For upper bound put something like
Post by: m@tty on December 13, 2009, 12:20:31 am
Isnt PDF if you want to find what proportion get a fixed value, whilst CDF will give you what proportion will get a range of values, hence the upper and lower bounds?When using a form of continuous probability like the bell curve probabilities are found by determining the area under the curve. The area under a curve at a single point is zero. Therefore you must always find the probability of a range of values occuring.
Post by: stonecold on December 13, 2009, 12:20:39 am
normCDF(49.5,10^10,30,7) gives 0.00267 which is 0.27%
Thanks m@tty!
Post by: kyzoo on December 13, 2009, 12:35:31 am
Post by: m@tty on December 13, 2009, 12:36:14 am
Post by: TrueTears on December 13, 2009, 12:38:04 am
PDF gives the "height" of the probability density function.Isnt PDF if you want to find what proportion get a fixed value, whilst CDF will give you what proportion will get a range of values, hence the upper and lower bounds?When using a form of continuous probability like the bell curve probabilities are found by determining the area under the curve. The area under a curve at a single point is zero. Therefore you must always find the probability of a range of values occuring.
Post by: vexx on December 13, 2009, 12:00:30 pm
i just did for 44, and i got 2.2% and for 45 its 1.6%
would this be correct?
Post by: m@tty on December 13, 2009, 12:17:13 pm
I remember reading in some VTAC publication [which I can't access now cause their site is screwed up] that Study scores are based upon a normal distribution of mean 30 and standard deviation 7 and is truncated at 0 and 50. I don't know exactly what that means, so ??? .
EDIT:
Have you seen this?
Quote from: VCAA
For studies with large enrolments (1,000 or more):
- 2% of students will get a score on or above 45
- 9% of students will get a score on or above 40
- 26% of students will get a score on or above 35
- 53% of students will get a score on or above 30
- 78% of students will get a score on or above 25
- 93% of students will get a score on or above 20.
and 400th post!!
Post by: vexx on December 13, 2009, 12:22:02 pm
isn't it odd then that it says 9% get 40+, when on the calc it says to 7.44%?
Post by: m@tty on December 13, 2009, 12:29:07 pm
Which will round to 9%, which is what they show.
normcdf(39.5,1000,30,7)=0.08736
Post by: vexx on December 13, 2009, 12:30:46 pm
I get 8.74%.
Which will round to 9%, which is what they show.
normcdf(39.5,1000,30,7)=0.08736
oh woops i didnt do the 1000 thing.
thanks heaps!
Post by: vexx on December 13, 2009, 06:04:33 pm
... wasting time .__.
ah, i just think i did it wrong, because apparently you need to go .5 less? so for 45, its 44.5, which is 1.9%
gah...
edit, i made a real one, check out nova's thread...
http://vcenotes.com/forum/index.php/topic,21207.msg215008.html#msg215008
Post by: kenhung123 on December 21, 2009, 08:35:55 pm