Calculate a trait frequency

Supplied materials

• All measurements and observations below are supplied classroom examples. They are not data from actual learners or a claim about a particular real site.
• Paper or browser document; an ordinary calculator is optional.
• Rule: Trait percentage equals 100 times trait count divided by total count. Formula: 100*a/b. Variable key: a = trait count, b = population count
• Distinct worked inputs and result: A distinct population has 12 of 40 individuals with a trait: 100×12/40=30%.
• Assessment case 1: Supplied case 1: trait count=15; population count=50, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?
• Assessment case 2: Supplied case 2: trait count=24; population count=60, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?
• Assessment case 3: Supplied case 3: trait count=18; population count=40, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?
• Assessment case 4: Supplied case 4: trait count=30; population count=75, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?
• Assessment case 5: Supplied case 5: trait count=36; population count=80, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?
• Assessment case 6: Supplied case 6: trait count=42; population count=70, using the explicitly named quantities. Trait percentage equals 100 times trait count divided by total count. What result follows?

Learn the idea

A frequency counts a specified category divided by a population total. A shift does not alone identify selection: sampling, migration and chance can also contribute.

Trait percentage equals 100 times trait count divided by total count. The formula in the supplied model is 100*a/b. Variable key: a = trait count, b = population count. Use total population as denominator. Count the same trait definition across intervals.

A distinct population has 12 of 40 individuals with a trait: 100×12/40=30%. A frequency change alone does not prove its cause. Track the quantity and unit before calculating. Explain the meaning of a positive, negative or fractional result when relevant. A numerical answer supports the stated model calculation; broader claims require the additional measurements and assumptions described here.

1. Name the measured quantities and their units before substituting values.
2. Write the stated rule and use the variable key to match each symbol to its explicitly named quantity.
3. Calculate each supplied case separately, keeping intermediate arithmetic and the result unit.
4. Explain the result in context and identify the assumption that would invalidate direct use of the rule.

Check your reasoning

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Take it further

Changed-input task: use the same stated model with trait count=16; population count=50. Expected result: 32 %. Explain what changes and keep this assumption: A frequency change alone does not prove its cause.

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