1. **State the problem:** We have a sample of 200 items, and 5 of them are defective. We want to estimate the percentage of defective items in the entire population. 2. **Formula used:** The percentage of defective items is calculated by \( \text{Percentage} = \frac{\text{Number of defective items}}{\text{Total number of items}} \times 100 \% \). 3. **Apply the formula:** Substitute the values: $$\text{Percentage} = \frac{5}{200} \times 100 = 2.5\%$$ 4. **Interpretation:** This means that based on the sample, we estimate that 2.5% of the items in the population are defective. 5. **Answer:** The estimated percentage of defective items in the population is **2.5%**.