NIMCET 2019
If the mean deviation of the numbers from their mean is 255, then d is equal to
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Answer: Option A — 10.1
Detailed Solution
There are 101 terms and the mean is the middle term .
The deviations are for ; their sum is .
MD .
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.⚠ Common trap
Taking 100 terms instead of 101 gives , which is not an option; count the terms from to .Quick tip
MD of an AP with terms
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Statistics — Preparation
This question tests your understanding of Statistics, a key topic in the Quantitative Aptitude section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
Statistics deals with collecting, summarising and interpreting data. This topic covers measures of central tendency (mean, median and mode) for ungrouped and grouped data, and measures of dispersion such as range, mean deviation, variance, standard deviation and the coefficient of variation. Exam questions test calculating these measures, the effect of adding or multiplying every observation by a constant, combined mean and variance of two groups, and comparing the consistency of two data sets. Remember that adding a constant to every value changes the mean but not the variance or standard deviation, while multiplying by k multiplies the standard deviation by |k|. Facts like these solve many questions without any calculation. Practise the statistics questions below, each with a step-by-step solution.