Revision Notes for Class 7 Maths Chapter 13: Connecting the Dots

Quick revision notes summarising all key concepts from Class 7 Maths Chapter 13 “Connecting the Dots” (mean, median, dot plots, and bar graphs). These Class 7 Mathematics Chapter 13 notes are ideal for quick revision just before exams.

• Mean (average) = (sum of all values) ÷ (number of values). It uses every value in the data set, so it can be pulled up or down a lot by unusually large or small values (outliers).
• Median = the middle value of a data set arranged in ascending (or descending) order. For odd n values, median = the ((n+1)/2)th term. For even n values, median = average of the (n/2)th and (n/2 + 1)th terms.
• Both the mean and the median of a data set always lie between its minimum and maximum values — neither can ever fall outside the data’s range.
• The median is often a better “typical value” than the mean when a data set has extreme outliers, since the mean is sensitive to outliers but the median is not.
• A dot plot shows each data value as a dot above a number line; repeated values are shown as stacked dots. It’s a simple, clear way to see the spread, clusters, and outliers in a small-to-medium data set.
• A bar graph uses bars of different heights/lengths to represent quantities for different categories, using a consistent scale (e.g. 1 unit = 25,000).
• A double-bar graph compares two related quantities (e.g. two groups, or two time periods) side by side for each category, using two different colours/patterns and a legend.
• To find “how many times more” one quantity is than another, always divide the larger value by the smaller one — never add or subtract them.
• To find the difference between two quantities (e.g. “how many more”), subtract the smaller value from the larger one.

See also: NCERT Solutions for Class 7 Maths Chapter 13

Practice more: Extra Questions for Class 7 Maths Chapter 13

For the full chapter, see the Class 7 Maths Formulas Handbook.

Written by Satish

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