Transforming Functions to Model Data

00:00 7 marks

  • Build Confidence
  • SL & HL
  • Tier 3
  • Data analysis
  • Scaling
  • Graph transformations
  • Horizontal shifts

A scientist is attempting to model measured data of a growth process using a base function. The base function is given by \(f(x) = e^x\).

(a) Determine the new function when the data indicates the growth is scaled vertically by a factor of 2.

(b) Adjust the function if the measurements show a horizontal shift to the right by 3 units.

(c) Compare the residuals of both models with the measured data and discuss which transformation provides a better fit and why.

Part a

3 minutes 2 marks

Question

Determine the new function when the data indicates the growth is scaled vertically by a factor of 2.



Hint Hint

Hint

Multiply the function by the scaling factor.

  • Answer Answer

Complete Answer

The new function is \(2e^x\).

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Part b

3 minutes 2 marks

Question

Adjust the function if the measurements show a horizontal shift to the right by 3 units.



Hint Hint

Hint

Replace \(x\) with \(x-3\) in the function.

  • Answer Answer

Complete Answer

Considering the scaling from part (a), the complete transformation is \(2e^{(x-3)}\).

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Part c

4 minutes 3 marks

Question

Compare the residuals of both models with the measured data and discuss which transformation provides a better fit and why.



Hint Hint

Hint

Discuss the closeness of the model predictions to the measured data based on residual differences.

  • Answer Answer

Complete Answer

The model \(2e^{(x-3)}\) is a better fit because the horizontal shift aligns the exponential growth phase with the data’s growth phase, reducing systematic errors in the residuals. For the model \(2e^x\), the residuals might show a pattern of consistently positive or negative values at the beginning or end of the data range, indicating a systematic deviation. By shifting the function horizontally, we aim to reduce this systematic pattern and achieve more randomly distributed residuals, which is a sign of a better fit.

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