Post by: Phresh on February 14, 2010, 11:59:08 pm
mean=100
standard deviation=15
97.5% of people taking the test will score more than __ ?
84% of people will score less than __?
How do i approach these questions?
Thank you
Post by: m@tty on February 15, 2010, 12:10:37 am
That's what was done in Methods, don't know for Further.
Post by: vexx on February 15, 2010, 12:12:22 am
Matty- this is further maths, it's easy to explain like this: hah
84% will score less then:
Well, one standard deviation above the mean is 115 and below is 85, and 68% of the people lie in this range. So if we were to say that less then 115 people score a certain percentage:
The number of people below the first standard deviation (85) is 16% yes? As there is 16% on either side of the first standard deviation (as 100%-68% is 32%) which means that 68% PLUS 16% is the total amount below 115, so that makes it 84%.
As for 97.5%
We know that two standard deviations either side of the mean is 95% (again using the 68-95-99.7 rule), so outside this standard deviation is 5% of the population, so on just one side of this is 2.5%, so we can say
100-30=70, (two standard deviations) and 70+ is 95% to 130 (115+15) and then above that is 2.5%
Therefore is 97.5%, so it is more than 70.
make sense?
Post by: m@tty on February 15, 2010, 12:26:20 am
Post by: the.watchman on February 15, 2010, 06:29:07 am
Post by: vexx on February 15, 2010, 02:18:23 pm
Post by: stonecold on February 15, 2010, 02:35:13 pm
Post by: Phresh on February 22, 2010, 05:56:04 pm
which is the independent and dependent variable?
Post by: vexx on February 22, 2010, 06:25:35 pm
Data showing the number of tourists visiting a small country in a month and the corresponding average monthly exchange rate for the country’s currency against the American dollar are given below.
which is the independent and dependent variable?
the number of tourists is the independent, and the exchange rate against the american dollar is the dependent as it depends on the number of tourists.
Post by: physics on February 22, 2010, 06:29:11 pm
ggggggggahhh she scares me :[
Post by: m@tty on February 22, 2010, 06:38:10 pm
But the number of tourists is also dependent on the exchange rate, more will go if it will be cheaper. Both effect each other, and exchange rate is more dependent on trade than tourism. ::)Data showing the number of tourists visiting a small country in a month and the corresponding average monthly exchange rate for the country’s currency against the American dollar are given below.
which is the independent and dependent variable?
the number of tourists is the independent, and the exchange rate against the american dollar is the dependent as it depends on the number of tourists.
Post by: the.watchman on February 22, 2010, 06:39:38 pm
But the number of tourists is also dependent on the exchange rate, more will go if it will be cheaper. Both effect each other, and exchange rate is more dependent on trade than tourism. ::)Data showing the number of tourists visiting a small country in a month and the corresponding average monthly exchange rate for the country’s currency against the American dollar are given below.
which is the independent and dependent variable?
the number of tourists is the independent, and the exchange rate against the american dollar is the dependent as it depends on the number of tourists.
True! But the tourists are dependent to a lesser extent... :P
Post by: m@tty on February 22, 2010, 06:44:29 pm
Post by: the.watchman on February 22, 2010, 06:46:14 pm
That's debatable.
Indeed! Hey Phresh, what does BoB say?
Post by: Phresh on February 22, 2010, 06:47:18 pm
Post by: the.watchman on February 22, 2010, 06:49:08 pm
As long as you know how to differentiate (:P) between the two different types of variables, then it doesn't really matter.
(I use the differentiate in normal English way too much :D)
Post by: vexx on February 22, 2010, 07:06:50 pm
number of tourists is the independent and the other is dependent. But my teacher says otherwise.. hrm
yeah that's correct.
matty- the exchange rate does not directly affect the tourists behaviour, they go when they please and themselves affect the exchanges, not the other way roundddddddd :p
Post by: the.watchman on February 22, 2010, 07:09:40 pm
number of tourists is the independent and the other is dependent. But my teacher says otherwise.. hrm
yeah that's correct.
matty- the exchange rate does not directly affect the tourists behaviour, they go when they please and themselves affect the exchanges, not the other way roundddddddd :p
But doesn't the exchange rate affect whether/where they want to travel or not?
Particularly if it makes costs cheaper/more expensive?
Post by: Visionz on February 22, 2010, 07:18:42 pm
Post by: the.watchman on February 22, 2010, 07:20:35 pm
I was doing independant and dependant variables today. I was like wtf. It said identify the dependant variable and I got every single question wrong. So I said I misread the question and put independant variables at the top. :P I think I know how to do it now...
LOL, independents do not change in relation to anything else (they DON'T DEPEND on anything)
Dependent variables change according to other variables (they DEPEND on something else)
Hope this helps!
Post by: m@tty on February 22, 2010, 07:23:51 pm
Post by: stonecold on February 22, 2010, 07:26:39 pm
question 9 core was nice kinda trick they played last year with independent variables:
http://www.vcaa.vic.edu.au/vcaa/vce/studies/mathematics/further/pastexams/2009/2009furmath1-w.pdf
question 8 core they fucked up on!!!! i hate you vcaa.