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Mathematics · unit version 1

Precalculus: semilog scales and model evidence

Construct and read logarithmic vertical axes, recover exponential models, and compare baseline assumptions using original-scale errors and unused predictions.

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Readiness and preparation

Check your starting point

Try these short questions on paper, then compare your reasoning. They are optional self-checks, not a placement score or a navigation requirement. Use a targeted review when useful and return with your browser’s Back control.

What happens to a logarithm when its positive input is multiplied by ten?

Logarithmic axes represent ratios rather than equal additive differences.

Compare reasoning and find a refresher

The base-ten logarithm increases by one: log₁₀(10u)=1+log₁₀u for u>0. Equal distances on a base-ten logarithmic axis therefore represent equal factors, not equal additions.

Review logarithm laws and positive inputs

Which quantity changes proportionally in a shifted exponential?

A baseline changes what belongs on a logarithmic axis.

Compare reasoning and find a refresher

In y=k+A b^x, the excess y−k is proportional across equal x steps. Taking log(y) generally does not remove the additive k. Subtracting a proposed baseline is a modeling decision that still needs evidence.

Review exponential baselines and evidence

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Semilog modeling: mixed practice

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Lesson sequence

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  1. Read semilog scales and test exponential evidence

    Lesson details and objectives

    Make the axis transformation visible, recover a response rule and evaluate what a straight-looking fit actually supports.

    • Place logarithmic vertical ticks and recover an exponential response from a line while keeping horizontal input spacing linear.
    • Execute an adjusted-response semilog fit with an explicit baseline, positive-domain checks and original-scale residual evidence.
    • Compare transformed criteria, physical units and unused predictions without treating finite visual linearity as proof.

    8 practice tasks.