Maths · Class 11 · Chapter 13
Statistics
11 lessons 90 min 2 simulations
Averages locate the centre of data; this chapter measures how the data spread around it. It starts from range, builds mean deviation about the mean and about the median for raw data, discrete frequency tables and class intervals, and explains why mean deviation is not enough. It then defines variance and standard deviation, computes them for raw and grouped data by the direct, alternative and step-deviation methods, and shows how shifting, scaling or correcting data changes them.
What the exam asks
Statistics is a steady JEE Main topic built almost entirely on the formulas of this chapter. Questions test mean deviation about the mean or median, variance and standard deviation of raw and grouped data, the effect of adding or multiplying by a constant, correcting a wrong observation, and finding missing observations from a given mean and variance. Marks are lost by forgetting to square the h in the shortcut, by using n in place of N, or by taking the square root of a variance too early or not at all.
Lessons
11 lessons · 90 min
1Why spread mattersNCERT §13.17 min2RangeNCERT §13.2, §13.37 min3Mean deviation for ungrouped dataNCERT §13.4, §13.4.111 min 1 sim4Mean deviation for discrete frequenciesNCERT §13.4.27 min5Mean deviation for class intervalsNCERT §13.4.27 min6From absolute values to squaresNCERT §13.4.3, §13.57 min7Variance and standard deviationNCERT §13.5, §13.5.16 min8Standard deviation of frequency distributionsNCERT §13.5.2, §13.5.36 min9Shortcut method for varianceNCERT §13.5.46 min10Shifting, scaling and correcting dataNCERT § "Miscellaneous Examples"11 min 1 sim11Chapter reviewMust-know facts, traps and formulas15 min