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6.4 Setting Up a Test for a Population Proportion

Part of Inference for Categorical Data: Proportions in AP® Statistics. Read the opening section, then create a free account for the full interactive lesson, practice, and progress tracking.

Writing Hypotheses

The null hypothesis H0{H_0}: A specific claim about the parameter (always has an "=" sign)
H0:p=p0H_0: p = p_0
where p0{p_0} is the claimed value.

The alternative hypothesis Ha{H_a}: Reflects what we're investigating:

  • Ha:p>p0{H_a: p > p_0} (one-sided, right-tailed)
  • Ha:p<p0{H_a: p < p_0} (one-sided, left-tailed)
  • Ha:p≠p0{H_a: p \neq p_0} (two-sided)

Rules for writing hypotheses:

  • H0{H_0} and Ha{H_a} are about the population parameter p{p}, not the sample statistic p^{\hat{p}}
  • State hypotheses before looking at the data
  • Use the context to determine if one-sided or two-sided is appropriate
Example: A political party claims support from a majority (more than 50%) of voters.
H0:p=0.50Ha:p>0.50H_0: p = 0.50 \quad H_a: p > 0.50

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