Responses to the Environment

AP Biology· difficulty 3/5

A student tests pillbug (Armadillidium vulgare) habitat preference using a two-chamber choice arena. Chamber A has moist filter paper; chamber B has dry filter paper. Twenty pillbugs are placed at the junction. After 10 minutes, the student counts how many are in each chamber. The trial is repeated five times with different pillbugs.

What is the null hypothesis for this experiment?

  • A

    Pillbugs prefer the dry chamber

  • B

    Pillbugs prefer the moist chamber

  • C

    Pillbugs distribute equally between moist and dry chambers

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  • D

    Pillbugs all aggregate in one chamber

Explanation

The null hypothesis (H0) for a binary choice test states no preference: 50/50 expected distribution. The data are then compared to this expectation, often with a chi-square goodness-of-fit test.

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