Step-by-Step Solution
Key Concept: $N = 50 \Rightarrow N/2 = 25$. Cumulative frequencies: 5, 15, 35, 43, 50. Median class is $20-30$ ($l=20, cf=15, f=20, h=10$). Median $= l + \left(\dfrac{N/2 - cf}{f}\right)h$.
Stepwise Solution:
Cumulative frequencies: $5, 15, 35, 43, 50$. $N = 50 \Rightarrow N/2 = 25$. [1.0 Mark]
Median class is $20-30$. $l=20, cf=15, f=20, h=10$. [0.5 Mark]
$\text{Median} = 20 + \left(\dfrac{25 - 15}{20}\right) \times 10 = 20 + \left(\dfrac{10}{20}\right) \times 10 = 20 + 5 = 25$. [1.5 Marks]
Marking Scheme:
• Preparing cumulative frequency column and finding $N/2 = 25$: 1.0 Mark
• Identifying median class $20-30$: 0.5 Mark
• Applying median formula to get $25$: 1.5 Marks
Correct Answer: