Capture recapture Q (2 Viewers)

[har]

http://community.boredofstudies.org/attachment.php?attachmentid=26813&d=1350971165
Was I meant to use 11% of the 2008 population or the 2012 one? I changed to 08 in last min

 

[harro619]

You were supposed to find out the 2008 pop size which was 11% more than in 2012. You couldn't simply do 240 X 1.11 but rather the method i used was 240/0.89 which gave 270 seals. Hope that helped.

 

[pb1234]

I used 240/100, and then x 111 to give 264?

 

[har]

Well I got 269.67 they better not take off a mark for not rounding up Fuck

 

[ofarrellt]

You gotta burn it to earn it.

 

[doormatt2012]

That question threw me. I ended up skipping that question because I just couldn't remember how to do capture-recapture, although I was taught it in both General Mathematics and Senior Science...

 

[emmkayyez]

I used trial and error LMAO and got an answer of 270. Totally forgot the capture-recapture formula even though I do biology =='

 

[lgnorance]

wtf how could you guys not get this. this is the easiest question in the whole exam.

 

[Focus is Key]

This is what I would do:

60x120 divided by 30 which gets you 240 seals. (Using the formula)

Now this is only 89% of 2008's total population. So then 240 divided by 89 (which gives 1%), then times by 100 to give you the desired amount which is 269.66..., rounding up to give 270 seals

 

[legallaura]

This is what I would do:

60x120 divided by 30 which gets you 240 seals. (Using the formula)

Now this is only 89% of 2008's total population. So then 240 divided by 89 (which gives 1%), then times by 100 to give you the desired amount which is 269.66..., rounding up to give 270 seals

yep i did exactly that.
and to those who didn't round.... um dont you have to???
you cant have .6629213 of a seal!!! they are like ppl and only come in whole numbers!!

 

[bakersdelight11]

i wrote the capture/recapture formula correctly, but in the midst, i experienced a coughing attack and suddenly substituted in the wrong numbers. do you think ill get marks for a follow through error?

 

[forgot]

i wrote the capture/recapture formula correctly, but in the midst, i experienced a coughing attack and suddenly substituted in the wrong numbers. do you think ill get marks for a follow through error?

good question, I think they might give it to you considering you knew how to do the steps and showed working out, but put in the wrong numbers.

 

[study-freak]

btw, did you guys get taught this population size estimation as a single 'formula' that you need to memorise?
I normally wouldn't call it a 'formula' to memorise.

Let M=total number of tagged seals, m=number of tagged seals in the sample, N=unknown population size, and n=sample size.
Then the sample estimate m/n (=proportion of tagged seals in the sample) should on average give M/N (=proportion of tagged seals in the population) given that you randomly sample the seals.
Hence N should be approximately nM/m.