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Define null hypothesis (H₀) in the context of two proportions.
Statement that there is no difference between the two population proportions being compared (p₁ = p₂).
Define alternative hypothesis (Hₐ) in the context of two proportions.
Statement that there *is* a difference between the two population proportions (p₁ ≠ p₂ , p₁ > p₂, or p₁ < p₂).
What is a z-score in hypothesis testing for two proportions?
A test statistic that measures how many standard deviations the observed difference in sample proportions is from the hypothesized difference (usually zero).
What is a p-value?
The probability of observing a sample difference as extreme as, or more extreme than, the one observed, assuming the null hypothesis is true.
Define significance level (α).
The probability of rejecting the null hypothesis when it is actually true (Type I error). Common values are 0.05 or 0.01.
What does it mean to 'reject the null hypothesis'?
It means there is sufficient evidence to conclude that there is a statistically significant difference between the two population proportions.
What are the differences between a one-sample z-test for proportions and a two-sample z-test for proportions?
One-sample: Compares a sample proportion to a hypothesized population proportion. Two-sample: Compares the proportions of two different samples to see if there's a difference between the populations.
What are the key differences between using the p-value and using the z-score to conclude a test?
P-value: Compare directly to the significance level (alpha). | Z-score: Assesses extremity using empirical rule (68-95-99.7 rule).
What are the differences between Type I and Type II errors?
Type I: Rejecting a true null hypothesis (false positive). | Type II: Failing to reject a false null hypothesis (false negative).
Explain the purpose of hypothesis testing for two proportions.
To determine if there is a statistically significant difference between the proportions of two populations based on sample data.
Explain how the p-value is used to make a conclusion in a hypothesis test.
The p-value is compared to the significance level (α). If the p-value is less than α, we reject the null hypothesis. If the p-value is greater than or equal to α, we fail to reject the null hypothesis.
Explain why we 'fail to reject' instead of 'accept' the null hypothesis.
Failing to reject the null hypothesis means we don't have enough evidence to say it's false, not that it's necessarily true. We haven't proven it, just failed to disprove it.
Describe the relationship between the z-score and the p-value.
The z-score is used to calculate the p-value. A larger absolute z-score corresponds to a smaller p-value, indicating stronger evidence against the null hypothesis.
What are the conditions for inference when comparing two proportions?
1. Random samples from each population. 2. Independent samples. 3. Large samples: n₁p₁, n₁(1-p₁), n₂p₂, n₂(1-p₂) all greater than or equal to 10.