Logistic Model Derivative Analysis

00:00 7 marks

  • Exam Style - Paper 2
  • SL & HL
  • Tier 4
  • Data analysis
  • Logistic growth
  • Derivative estimation

A research team collected population data of a species at different time intervals. The data collected is as follows:

Time (years) Population
0 500
2 800
4 1200
6 1500
8 1700

Using this dataset:
(a) Estimate the instantaneous rate of change of the population at t = 4 years using a central difference method.
(b) Assuming the population follows a logistic model given by \(P(t)=\frac{2000}{1+Ae^{-rt}}\) with a carrying capacity of 2000, use your derivative estimate from part (a) to refine the estimate for the growth rate \(r\) at t = 4 years.

Part a

4 minutes 3 marks

Question

Using the provided data, estimate the instantaneous rate of change of the population at t = 4 years using the central difference method with h = 2 years.



Hint Hint

Hint

Apply \(\frac{f(t+h)-f(t-h)}{2h}\) with h = 2 using the values f(2)=800 and f(6)=1500.

  • Answer Answer

Complete Answer

Approximately 175 individuals per year

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Part b

6 minutes 4 marks

Question

Assuming the logistic model \(P(t)=\frac{2000}{1+Ae^{-rt}}\) applies, use your derivative estimate from part (a) to refine the estimate for the growth rate \(r\) at t = 4 years. Hint: First, use the initial condition P(0) = 500 to find the value of A. Then, differentiate the logistic model to relate \(P'(t)\) with \(r\).



Hint Hint

Hint

First, use P(0) = 500 to find A. Differentiate \(P(t)\) and equate \(P'(4)\) to 175, then solve approximately for \(r\).

  • Answer Answer

Complete Answer

Approximately 0.3 per year

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