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Part ACSIR NET June 2024same-mean-different-spread

Same mean different spread

The diagrams show the distribution of trees in two forest patches A and B. Each patch is divided into smaller “quadrats”. The number of trees in each quadrat is shown. Which one of the following statements about the means (μ)(\mu) and standard deviations (σ)(\sigma) of the numbers of trees in the two patches is true?

Forest Patch A
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1
1 1 1 1 1

Forest Patch B
2 0 0 0 0
0 0 0 0 0
0 0 0 7 0
0 10 0 0 0
0 0 0 0 6
  1. A.μ(A)=μ(B),σ(A)=σ(B)\mu(A) = \mu(B), \sigma(A) = \sigma(B)
  2. B.μ(A)>μ(B),σ(A)>σ(B)\mu(A) > \mu(B), \sigma(A) > \sigma(B)
  3. C.μ(A)=μ(B),σ(A)<σ(B)\mu(A) = \mu(B), \sigma(A) < \sigma(B)✓ Correct
  4. D.μ(A)<μ(B),σ(A)<σ(B)\mu(A) < \mu(B), \sigma(A) < \sigma(B)

You have the answer. Trap Analysis is why the other three were written.

Not a worked solution repeated four times — the specific reasoning error each wrong option was built to reward, and why this one tests invariants don't determine.

See pricing

50 are analysed free — try those first.

The trap it tests

Invariants don't determine

Two objects sharing an invariant were treated as the same object.

Drill statements like this

Last revised . Found a mistake? Tell us — corrections are the fastest thing we act on.

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