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The question asks how many more Year 9 students than Year 8 students should be included in the survey, given the total number of students in each year group and that Mr. Ford wants to survey 50 students stratified by year group.

### Steps to solve:

1. **Total number of students**: 350 students (from Year 7, 8, and 9 combined).
2. **Year 9 students**: 160 students.
3. **Year 8 students**: 110 students.

Mr. Ford will survey 50 students. The number of students surveyed from each year group should be proportional to the number of students in that year group relative to the total.

4. **Year 9 proportion**:  
   \( \text{Year 9 proportion} = \frac{160}{350} \)
5. **Year 8 proportion**:  
   \( \text{Year 8 proportion} = \frac{110}{350} \)

6. Multiply the proportions by 50 to find out how many Year 9 and Year 8 students will be in the survey:
   - Number of Year 9 students in the survey:  
     \( \frac{160}{350} \times 50 \)
   - Number of Year 8 students in the survey:  
     \( \frac{110}{350} \times 50 \)

7. Finally, subtract the number of Year 8 students from the number of Year 9 students to get how many more Year 9 students should be included in the survey compared to Year 8.

Let's calculate this.The survey should include approximately 7 more Year 9 students than Year 8 students.

Would you like more details or explanations on this solution?

Here are 5 related questions:
1. How would the number of Year 7 students in the survey be calculated?
2. What is the total proportion of Year 9 students in the entire group of 350?
3. How can stratified sampling be used for larger or smaller surveys?
4. What if the total number of students was different—how would the survey size change?
5. How does changing the number of students surveyed affect the proportions?

**Tip:** Stratified sampling ensures that the sample represents the population's different subgroups proportionally, improving the accuracy of results.

How many more Year 9 students than Year 8 students should be in the survey?

Learn how to calculate how many more Year 9 students than Year 8 students should be included in a stratified survey, based on their proportions in the overall population. This problem involves proportional sampling, stratified sampling, and subtraction. Suitable for students in Grade 7-9.

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