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GeographyClass 12them comprehensible. It facilitates data processing. A number of statistical

them comprehensible. It facilitates data processing. A number of statistical | Class 12 Geography Notes

By ConceptScroll Team · Published on 17 July 2026 · 3 min read

them comprehensible. It facilitates data processing. A number of statistical – this guide gives you a concise, exam-ready overview of them comprehensible. It facilitates data processing. A number of statistical from Class 12 Geography, written by ConceptScroll editors and reviewed against the latest NCERT textbook.

Mean

The mean is the arithmetic average of a set of values. It is calculated by summing all the observations and dividing the total by the number of observations. The mean provides a central value that represents the entire data set. There are different methods to compute the mean depending on whether the data is ungrouped or grouped. For ungrouped data, the direct method involves adding all values and dividing by the count. For large data sets or grouped data, indirect methods involving assumed means and deviations are used to simplify calculations. The mean is sensitive to extreme values and is widely used in geographical data analysis to summarize variables like rainfall, wages, or population.

📊 Diagram: No specific diagram, but Table 2.1 illustrates rainfall data and calculations for mean using both direct and indirect methods.

🔗 Connection: This section introduces mean, leading to detailed computation methods for ungrouped and grouped data in subsequent sections.

Frequently asked questions

1. Choose the correct answer from the four alternatives given below: (i) The measure of central tendency that does not get affected by extreme values: (a) Mean (b) Mean and Mode (c) Mode (d) Median (ii) The measure of central tendency always coinciding with the hump of any distribution is: (a) Median (b) Median and Mode (c) Mean (d) Mode

(i) The measure of central tendency that does not get affected by extreme values is the Median (d). Mean is affected by extreme values, Mode is not necessarily unaffected. Median is resistant to extreme values.

(ii) The measure of central tendency always coinciding with the hump of any distribution is the Mode (d). The Mode is the value that appears most frequently and corresponds to the peak (hump) of the distribution.

2. Answer the following questions in about 30 words: (i) Define the mean. (ii) What are the advantages of using mode?

(i) Mean is the sum of all observations divided by the number of observations. It represents the average value of the data set.

(ii) Advantages of mode:

  • It is easy to understand and calculate.
  • It can be used for qualitative data.
  • It represents the most common value in the data set.
  • It is not affected by extreme values.
3. Answer the following questions in about 125 words: (i) Explain relative positions of mean, median and mode in a normal distribution and skewed distribution with the help of diagrams. (ii) Comment on the applicability of mean, median and mode (hint: from their merits and demerits).

(i) In a normal distribution, mean = median = mode, all three measures coincide at the center of the symmetric bell-shaped curve.

In a positively skewed distribution, mode < median < mean. The tail is stretched to the right, so mean is pulled towards higher values.

In a negatively skewed distribution, mean < median < mode. The tail is stretched to the left, so mean is pulled towards lower values.

Diagrams typically show the bell curve for normal distribution and skewed curves with shifted pea

Activity 1. Take an imaginary example applicable to geographical analysis and explain direct and indirect methods of calculating mean from ungrouped data.

Direct Method: Suppose the data set of ungrouped data is: 5, 7, 9, 10, 12. Mean = (5 + 7 + 9 + 10 + 12) / 5 = 43 / 5 = 8.6

Indirect Method: Choose an assumed mean (A), say 9. Calculate deviations d = x - A: (-4, -2, 0, 1, 3) Sum of deviations Σd = (-4) + (-2) + 0 + 1 + 3 = -2 Mean = A + (Σd / n) = 9 + (-2/5) = 9 - 0.4 = 8.6

Both methods yield the same mean value.

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