1. **State the problem:** We want to find the proportion of students in the sample who believe that "social media has a negative effect on my day-to-day happiness" in 2024. 2. **Formula used:** The proportion $P$ is calculated by dividing the number of students who believe the statement by the total number of students surveyed: $$P = \frac{\text{frequency}}{\text{total number}}$$ 3. **Apply the formula:** Given frequency = 150 and total number = 250, $$P = \frac{150}{250} = 0.6$$ 4. **Interpretation:** The proportion is 0.6, which means 60% of the surveyed students believe social media negatively affects their happiness. 5. **Rounding:** The proportion rounded to two decimal places is $0.60$. **Final answer:** The proportion of people in the sample who believed that social media has a negative effect on their day-to-day happiness in 2024 is $0.60$.