Statistics
RD Sharma
CBSE
Grade 10
Question:
Calculate the mean of the following distribution:
Marks: 0-10, 10-20, 20-30, 30-40, 40-50
Students: 12, 16, 6, 0, 6
Step-by-Step Solution
Key Concept: $x_i$: 5, 15, 25, 35, 45.<br>$f_i x_i$: 60, 240, 150, 0, 270.<br>$\sum f = 40, \sum f x = 720$.<br>$\bar{x} = 720 / 40 = 18.0$.
$\sum f_i = 40$. [0.5 Mark]
$\sum f_i x_i = 60 + 240 + 150 + 0 + 270 = 720$. [1.5 Marks]
$\bar{x} = 720 / 40 = 18.0$. [1.0 Mark]
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🎯 Official CBSE Marking Scheme:
Calculating $\sum f_i = 40$: 0.5 Mark
Calculating $\sum f_i x_i = 720$: 1.5 Marks
Evaluating mean $= 18.0$: 1.0 Mark
Correct Answer:
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