1. **State the problem:** We want to test if more than 3% of all 1-pound packages are underweight based on a sample where 4% were underweight.
2. **Set hypotheses:**
- Null hypothesis $H_0: p = 0.03$ (proportion underweight is 3%)
- Alternative hypothesis $H_a: p > 0.03$ (proportion underweight is greater than 3%)
3. **Sample data:**
- Sample size $n = 1000$
- Sample proportion $\hat{p} = \frac{40}{1000} = 0.04$
4. **Test statistic formula for proportion:**
$$z = \frac{\hat{p} - p_0}{\sqrt{\frac{p_0(1-p_0)}{n}}}$$
where $p_0 = 0.03$ is the hypothesized proportion.
5. **Calculate standard error:**
$$SE = \sqrt{\frac{0.03 \times (1 - 0.03)}{1000}} = \sqrt{\frac{0.03 \times 0.97}{1000}} = \sqrt{0.0000291} \approx 0.0054$$
6. **Calculate z-score:**
$$z = \frac{0.04 - 0.03}{0.0054} = \frac{0.01}{0.0054} \approx 1.85$$
7. **Find p-value:**
Since this is a right-tailed test, p-value = $P(Z > 1.85)$. Using standard normal tables or calculator, p-value $\approx 0.032$.
8. **Decision rule:**
At significance level $\alpha = 0.05$, if p-value $< 0.05$, reject $H_0$.
9. **Conclusion:**
Since $0.032 < 0.05$, we reject the null hypothesis and conclude there is convincing evidence that more than 3% of packages are underweight.
**Answer:** B Yes, because the p-value of 0.032 is less than the significance level of 0.05.
Hypothesis Testing Proportions Ca0200
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