Question:medium

If \( \sum_{i=1}^{10} (x_i - 3) = 7 \) and \( \sum_{i=1}^{10} (x_i - 3)^2 = 27 \), then the standard deviation of the 10 items is

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Shifted data formulas reduce heavy calculations in statistics.
Updated On: Apr 22, 2026
  • 2.547
  • 1.87
  • 14.86
  • 1.486
Show Solution

The Correct Option is D

Solution and Explanation

Step 1: Understanding the Concept:
The standard deviation (\( \sigma \)) of a set of data is independent of the origin. Shifting the data by subtracting a constant (like 3) does not change the standard deviation.
Step 2: Key Formula or Approach:
Let \( y_i = x_i - 3 \). Then standard deviation is:
\[ \sigma = \sqrt{\frac{\sum y_i^2}{n} - \left(\frac{\sum y_i}{n}\right)^2} \]
Step 3: Detailed Explanation:
Given \( n = 10 \), \( \sum y_i = 7 \), and \( \sum y_i^2 = 27 \).
\[ \sigma = \sqrt{\frac{27}{10} - \left(\frac{7}{10}\right)^2} \]
\[ \sigma = \sqrt{2.7 - (0.7)^2} = \sqrt{2.7 - 0.49} \]
\[ \sigma = \sqrt{2.21} \]
Calculating the square root:
\( \sqrt{2.21} \approx 1.4866 \).
Step 4: Final Answer:
The standard deviation is 1.486.
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