NCERT Mathematics, Class 11, textbook pages 257–288

How to help your child with Class 11 Maths Chapter 13, Statistics, at home

Dispersion: mean deviation, variance and standard deviation, explained for parents: a 45-minute study session, a quick challenge, a 5-day plan and the mistakes to watch for.

same mean, different spread

NCERT Class 11 Maths Chapter 13 Statistics: what it teaches

Two classes can have the same average but different spread. Your teen measures dispersion with range, mean deviation, variance and standard deviation, and compares variability with the coefficient of variation.

Why it matters later. Statistics leads to probability distributions in Class 12 and data science.

See it: this chapter in pictures

3, 5, 7, 9, 11 (mean 7)|deviations|: 4, 2, 0, 2, 4MD = 12/5 = 2.4
Average distance from the mean.
variance = (16+4+0+4+16)/5= 8SD = √8 = 2√2
SD is the square root of variance.
CV = SD/mean × 100lower CV= more consistent
Compare consistency fairly.

You need

  • a calculator
  • two sets of real data (like cricket scores)

Tonight’s 45 minutes

  1. Two batters average 40. Compare their scores’ spread.
  2. Find the mean deviation about the mean for 3, 5, 7, 9, 11 (2.4).
  3. Find the variance and standard deviation of the same data (8, 2√2).
  4. Compare consistency with the coefficient of variation.

Words to use

  • range
  • mean deviation
  • variance
  • standard deviation
  • coefficient of variation

Watch for

  • Forgetting absolute values in mean deviation. Use |x − mean|.
  • Mixing variance and standard deviation. SD is the square root of variance.

What it sounds like at home

A short example of the conversation. Your words will differ; the questions are what matter.

YouSame average, who’s more consistent?

Your childThe one with smaller standard deviation.

A game for this week: Consistency test

  1. Collect scores of two players over 10 matches.
  2. Compute mean and SD.
  3. Compare CVs.
  4. Decide who is more consistent.

A 5-day plan, 45 minutes a day

  1. Day 1Explain-back.
  2. Day 2Worked examples.
  3. Day 3Practice set.
  4. Day 4Real-life problem.
  5. Day 5Mixed quiz.

Everyday moments to practise

  • Cricket averages.
  • Quality control.
  • Exam results.
  • Weather variability.

Quick check

Ask these at the end of the week. Tap to see the answer.

Mean deviation of 3, 5, 7, 9, 11 about mean?

2.4.

Variance of the same?

8.

Lower CV means?

More consistent.

Ready for the next chapter when your child…

  • Computes measures of dispersion.
  • Interprets SD and CV.
  • Compares datasets.

Activities, wording and illustrations are Mathify Kids’ own, following the topics of NCERT’s Mathematics (Class 11). See the full Class 11 parent guide for every chapter.

Questions parents ask

What is standard deviation?

The square root of the average squared distance from the mean.

Why square deviations?

To avoid positive and negative deviations cancelling.

What is the coefficient of variation?

SD ÷ mean × 100, used to compare consistency.