JEE Mains · Maths · STD 11 - 13. statistics
If for some \(x \in R\), the frequency distribution of the marks obtained by \(20\) students in a test is
Marks \(2\) \(3\) \(5\) \(7\)
Frequency \((x+1)^2\) \(2x -5\) \(x^2 -3x\) \(x\)
Then the mean of the marks is
- A \(2.8\)
- B \(3.2\)
- C \(2.5\)
- D \(3\)
Answer & Solution
Correct Answer
(A) \(2.8\)
Step-by-step Solution
Detailed explanation
\(\bar x = \frac{{\sum {{x_i}{f_i}} }}{{\sum {{x_i}} }}\) \(\because\) \(\sum {{f_i}} = {\left( {x + 1} \right)^2} + \left( {2x - 5} \right) + \left( {{x^2} - 3x} \right) + x = 20\) \( \Rightarrow x = 3, - 4\) (rejected)…
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