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To estimate the population in a rookery, 4965 fur seal pups were captured and tagged in early August. In late August, 900 fur seal pups were captured. Of these, 218 had been tagged. Based on these figures, estimate the population of fur seal pups in the rookery. [Source: Chapman and Johnson, "Estimation of Fur Seal Pup Populations by Randomized Sampling," Transactions of the American Fisheries Society, 97 (July 1968), 264-270.

Short Answer

Expert verified
The estimated population of fur seal pups in the rookery is approximately 20477.

Step by step solution

01

Understanding the Proportions

We know two ratios from the description: the number of tagged seals to the total initial tagging count, and the number of tagged seals in the recaptured sample to the recaptured sample size. These ratios are expected to be equal, as they both represent the ratio of 'tagged seals to total seals' in the rookery, at different times.
02

Setting Up the Equation

The proportion can be represented as: \(\frac{{\text{{tagged seals in initial count}}}}{{\text{{total initial count}}}} = \frac{{\text{{tagged seals in recaptured sample}}}}{{\text{{recaptured sample size}}}}\). Substituting from the problem, we have \(\frac{4965}{x} = \frac{218}{900}\), where \(x\) is the total population we're trying to estimate.
03

Solving the Equation

To solve for \(x\), we can cross multiply and simplify to obtain \(x = \frac{(4965 * 900)}{218} = 20477.06\). Since we can't have a fraction of a seal pup, we should round this off to the nearest whole number.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Proportional Reasoning
Proportional reasoning is a key concept when determining the population size using tag-recapture methods. Essentially, we are looking at maintaining the balance between two ratios.
In this case, proportional reasoning helps us understand that the tagged proportion of seals in our initial group should match the ratio of tagged seals in any subsequent sample we take.
  • The ratio of tagged seals to total seals in the initial period is 4965 (tagged seals) to the unknown total population.
  • We then assume that this ratio is maintained when we draw another sample, which includes 218 tagged seals out of 900 total seals caught.
By setting up an equation that equates these two proportions, we effectively use proportional reasoning to solve for the unknown total population. This method ensures that our estimations are based on logical reasoning, thereby reducing error margins.
Sampling Methods
When estimating wildlife population, sampling methods like tag-recapture are critical for effective data collection. This exercise uses a specific form of sampling called the "capture-recapture" method. This approach helps estimate populations when a complete census (count of every individual) is impractical.
The process involves:
  • Capturing a sample of the population and tagging them (4965 pups, in this case).
  • Releasing them back into the wild to mix with the rest of the population.
  • Later, another sample is captured (900 pups), and the number of tagged individuals (218 pups) is noted.
This method assumes a constant population during the time period between samplings, no tags have fallen off, and each individual has an equal chance of being captured again. Using these assumptions, we apply proportional reasoning to extract accurate population estimates.
Mathematical Modeling
Mathematical modeling involves using mathematical expressions to represent real-world phenomena. In this context, we aim to model the population of fur seal pups using the tag-recapture method.
The model setup uses a simple proportion equation:\[\frac{\text{Initial tagged}}{\text{Total estimated population}} = \frac{\text{Recaptured tagged}}{\text{Recaptured sample size}}\]This proportion allows us to represent the relationship between the tagged seals and the estimated total population.
After setting up the model as \(\frac{4965}{x} = \frac{218}{900}\), solving the equation requires algebraic manipulation: cross-multiplying to find \(x\), which is the estimated total population. This approach makes use of algebra not only to project populations but also to encapsulate the underlying biological processes in numerical form, guiding conservation efforts with clear data.

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Most popular questions from this chapter

Today, most consumer marketing surveys are conducted by telephone. In selecting a sample of households that are representative of all the households in a given geographical area, the two basic techniques used are (1) randomly selecting telephone numbers to call from the local telephone directory or directories and (2) using a computer to randomly generate seven-digit numbers to try that are compatible with the local phone numbers. (a) Briefly discuss the advantages and disadvantages of each technique. In your opinion, which of the two will produce the more reliable data? Explain. (b) Suppose that you are trying to market burglar alarms in New York City. Which of the two techniques for selecting the sample would you use? Explain your reasons.

Madison County has a population of 34,522 people. The county hospital is interested in estimating the number of people in the county with blood-type \(A-\). To do this they test blood samples from 253 patients. Out of this group, 17 have blood-type \(A-\) Use this sample to estimate the number of people in Madison County with blood-type \(\mathrm{A}-\).

Refer to the following story: The 1250 students at Eureka High School are having an election for Homecoming King. The candidates are Tomlinson (captain of the football team), Garcia (class president), and Marsalis (member of the marching band). At the football game a week before the election, a pre- election poll was taken of students as they entered the stadium gates. Of the students who attended the game, 203 planned to vote for Tomlinson, 42 planned to vote for Garcia, and 105 planned to vote for Marsalis. (a) Compare and contrast the population and the sampling frame for this survey. (b) Is the sampling error a result of sampling variability or of sample bias? Explain

Refer to a landmark study conducted in 1896 in Denmark by Dr. Johannes Fibiger, who went on to receive the Nobel Prize in Medicine in \(1926 .\) The purpose of the study was to determine the effectiveness of a new serum for treating diphtheria, a common and often deadly respiratory disease in those days. Fibiger conducted his study over a one-year period (May 1896-April 1897) in one particular Copenhagen hospital. New diphtheria patients admitted to the hospital received different treatments based on the day of admission. In one set of days (call them "even" days for convenience), the patients were treated with the new serum daily and received the standard treatment. Patients admitted on alternate days (the "odd" days) received just the standard treatment. Over the one-year period of the study, eight of the 239 patients admitted on the "even" days and treated with the serum died, whereas 30 of the 245 patients admitted on the "odd" days died. (a) Describe the control and treatment groups in Fibiger's study. (b) What conclusions would you draw from Fibiger's study? Explain.

You want to estimate how many fish there are in a small pond. Let's suppose that you first capture \(n_{1}=500\) fish, tag them, and throw them back into the pond. After a couple of days you go back to the pond and capture \(n_{2}=120\) fish, of which \(k=30\) are tagged. Estimate the number of fish in the pond.

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