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NDA 2020 Maths · Mathematics · Statistics · medium

The median of a set of observations is always one of the observations. 2. The standard deviation does not change if the same constant is added to…

Single correct option

Consider the following statements:
1. The median of a set of observations is always one of the observations.
2. The standard deviation does not change if the same constant is added to every observation.
Which of the statements is/are correct?
  1. A. 1 only
  2. B. 2 only
  3. C. Both 1 and 2
  4. D. Neither 1 nor 2
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Answer: (B) 2 only

For an even number of observations the median is the average of the two middle values, which need not be an observation (the median of 1,2,3,41,2,3,4 is 2.52.5). So statement 1 is false. Adding a constant shifts every observation and the mean by the same amount, so the deviations from the mean are unchanged and the standard deviation stays the same. Statement 2 is correct. Spread measures are unaffected by shifts but scale with multiplication.
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Original question written in the NDA 2020 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake