questions

[Phresh]

Hi

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

[m@tty]

In calculator use then convert from z-score
That's what was done in Methods, don't know for Further.

[vexx]

Hi

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?

[m@tty]

Oh, didn't realise they were part of the 68-95-99.7 rule, I thought about it, but failed to see the symmetry.

[the.watchman]

Lol, I made the same mistake in another thread, using MM techniques

[vexx]

Haha, it's so much easier using the further rule, and it can all be easily done without much thought

[stonecold]

make sure you're familiar with the normal distribution and the 68-95-99.7 rule (i think those are the numbers haha!), as it is guaranteed to appear on the exam.

[Phresh]

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?

[vexx]

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.

[physics]

teacher said not to use the methods technique..... apparently she looks down on me because i did methods last year and chose to do further
ggggggggahhh she scares me :[

[m@tty]

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.

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. 

[the.watchman]

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.

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. 

True! But the tourists are dependent to a lesser extent...

[m@tty]

That's debatable.

[the.watchman]

That's debatable.

Indeed! Hey Phresh, what does BoB say?

[Phresh]

number of tourists is the independent and the other is dependent. But my teacher says otherwise.. hrm