Ch 3 covers data collection, organisation, and representation. Students learn measures of central tendency (mean, median, mode), represent data using bar graphs and double bar graphs, and get introduced to the concept of probability.
Mean (average) = sum of all observations ÷ total number of observations. Median is the middle value of ordered data. Mode is the value that appears most frequently. Each measure provides different insights into data.
Bar graphs display data using rectangular bars. Double bar graphs compare two related data sets side by side. Both have categories on one axis and values on the other.
Probability measures the chance of an event occurring. Probability = number of favourable outcomes ÷ total number of outcomes. Probability ranges from 0 (impossible) to 1 (certain).
Download: https://ncert.nic.in/textbook/pdf/gemh103.pdf | Complete book: https://ncert.nic.in/textbook/pdf/gemh1ps.zip
Mean is the arithmetic average of all values. Median is the middle value when data is arranged in order. Median is less affected by extreme values (outliers) than mean.
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