Macaroni Mark-recapture

In this lab, Group 5 examined the Mark-recapture Sampling Technique used to estimate population size.

In our Second trial, 100 pastas were "captured" from a baggie.

They were each marked with the design that included 3 circles.

The 100 marked pastas were then "released" back into the baggie, then mixed together.

Now, 100 pastas are randomly selected, and the number of marked pastas is recorded at 14.

The population size is then calculated using the formula: # of pastas captured & marked/population size= # of marked pastas recaptured/total # of pastas recaptured

Using the formula, we found that the estimated population size was 714. We had also counted the total number of pastas that were in the baggie, which was 615.

We used the same procedures in our 1st trial, however we marked 40 pastas and recaptured 45 in total, and found 1 that was marked. That estimated population size worked out to be 1800, way off from the actual count.

Analysis:

1. To compare the size of the population using the Mark-recapture method vs the true size, we calculated the margin of error using the formula: % error= (Theoretical size- Exprimental size)/Theoretical size.

We found that the margin of error for the 2nd trial was 16%, while it was 104% with the average of both the 1st and 2nd trials. Therefore we ruled the 1st trial as an outlier. We suspect that the reason that the 1st trial was so far off was because we did not mark that many pastas compare to total amount of pasta, and also it may not have been mixed well before we recaptured.

Overall, the estimate and the true size were pretty close, a difference of 99, and it was a little less tedious to use the Mark-recapture method.

2. a) There are many problems that could affect the accuracy of our estimate, including not having marking enough individuals relative to the total population size, which we did, where we got many unmarked pastas compared to marked. Other problems may be incomplete mixing, and the probability of recapturing a completely evenly distributed sample.

b) Ecologists using the Mark-recapture method with animal popuations may encounter problems like animals migrating, the tags falling off, capturing and tagging enough individuals, and naturals disasters that may kill mass populations.

3. To get more accurate data, we could conduct more trials and combine the information, capture and mark more pastas, and finally mix the baggie more throughoutly.