Project Maths Paper 2 2010 Question 9A (c)

FaoiSin

In the Project Maths Paper 2 2010 Q9A part (c) is a strange question. The hypothesis questions in the books are very simple just add or minus the Margin Of Error. Would anybody be able to explain this one to me please?

It's on p53 of this:

http://www.examinations.ie/archive/markingschemes/2010/LC003ALP030EV.pdf

ChemHickey

YeaaahFaoiSin wrote: »

In the Project Maths Paper 2 2010 Q9A part (c) is a strange question. The hypothesis questions in the books are very simple just add or minus the Margin Of Error. Would anybody be able to explain this one to me please?

It's on p53 of this:

http://www.examinations.ie/archive/markingschemes/2010/LC003ALP030EV.pdf

It's not on our course. We'll be just getting the simple ones!

Thoie

It's been an extremely loooong time since I've looked at anything like that, so I may have calculated things incorrectly, but the 0.2 looks odd to me. From my calculations I got 0.236854386 (in Excel). That does round to 0.2, but it throws off the rest of the calcs.

Using 0.2/sqrt(10) you get 0·0632456 as they state.
If you use 0.236854386/sqrt(10) you get 0.074899933


This changes the value of z - with "my" number I'd conclude the machine is accurate

MathsManiac

Thoie wrote: »

It's been an extremely loooong time since I've looked at anything like that, so I may have calculated things incorrectly, but the 0.2 looks odd to me. From my calculations I got 0.236854386 (in Excel). That does round to 0.2, but it throws off the rest of the calcs.

Using 0.2/sqrt(10) you get 0·0632456 as they state.
If you use 0.236854386/sqrt(10) you get 0.074899933


This changes the value of z - with "my" number I'd conclude the machine is accurate

The population standard deviation is known to be 0.2, so there's no need to use the sample to estimate it.

(But as ChemHickey says, this is not on the course for the current LC students.)

Also, by the way, if you were going to use the sample to estimate the standard deviation, you should really use the "n-1" version of the formula, which would have given you 0.249666444 rather than 0.236854386.

Thoie

MathsManiac wrote: »

The population standard deviation is known to be 0.2, so there's no need to use the sample to estimate it.

And this, children, is a lesson in why it's important to read all parts of the question carefully before answering.