Capture/Recapture Question (1 Viewer)

[frenzal_dude]

Huong used the 'capture-recapture' technique to estimate the number of trout living in a dam.

She caught, tagged and released 20 trout.
Later she caught 36 trout at random from the same dam.
She found that 8 of these 36 trout had been tagged.

What estimate should Huong give for the total number of trout living in this dam, based on her use of the capture recapture technique?

A) 56
B) 90
C) 160
D) 162

 

[pqd123]

so if 8 of the 36 trout were tagged, then 8/36 of the total trout in the dam should be tagged. Therefore 20 is equal to 8/36 of the total number of trout. dividing 20 by 8/36 gives you 90, so b.

 

[mioumiou]

Huong used the 'capture-recapture' technique to estimate the number of trout living in a dam.

She caught, tagged and released 20 trout.
Later she caught 36 trout at random from the same dam.
She found that 8 of these 36 trout had been tagged.

What estimate should Huong give for the total number of trout living in this dam, based on her use of the capture recapture technique?

A) 56
B) 90
C) 160
D) 162

Is the answer B? I think I've got B

 

[frenzal_dude]

it's from 2009 hsc paper, there's no answers given, but if you both got B then it must be right.

 

[fullonoob]

so if 8 of the 36 trout were tagged, then 8/36 of the total trout in the dam should be tagged. Therefore 20 is equal to 8/36 of the total number of trout. dividing 20 by 8/36 gives you 90, so b.

ye
i remember doing this in yr 10

 

[bbychocoholic]

ye
i remember doing this in yr 10

it's also in the biology prelim course.

this is how i work it out and how i learnt it in both maths and bio:
it's a lil different to the other method but i got the same answer.

FORMULA:

number recaptured x number tagged in first capture / number tagged from recapture.

so in this case it would be:

36 x 20 / 8
= 90

 

[Kat92]

it's also in the biology prelim course.

this is how i work it out and how i learnt it in both maths and bio:
it's a lil different to the other method but i got the same answer.

FORMULA:

number recaptured x number tagged in first capture / number tagged from recapture.

so in this case it would be:

36 x 20 / 8
= 90

This is the way that our classes learnt it. However, pick a style that best suits you. It doesn't matter which method that you use as long as you feel comfortable and can obtain the correct answer.