Chapter 13: Connecting the Dots…
Data is everywhere, from cricket scores to onion prices and heights. In this chapter we learn which questions need data, summarise data with the mean and the median, see how outliers affect them, picture data with dot plots and double bar graphs, and act as data detectives who only claim what the data supports.
In this chapter you will
- recognise statistical questions
- find and compare the mean and the median
- read and draw dot plots and double bar graphs
- draw only justified conclusions from data
Topics
- Of Questions and Statements NCERT P2 5.1
A statistical question is answered by collecting data that varies.
- Representative Values NCERT P2 5.2
Mean = sum ÷ count (a fair share); median = the middle of the sorted values.
- Visualising Data NCERT P2 5.3
A double bar graph puts two bars per category side by side to compare two groups.
- Data Detective NCERT P2 5.4
Use data to justify claims; averages describe groups, not every individual.
Key words
- Statistical question
- a question answered by collecting data that varies
- Mean
- sum of the values ÷ number of values
- Median
- the middle value of sorted data
- Outlier
- a value far away from the rest
- Dot plot
- dots stacked above a number line, one per value
- Double bar graph
- two bars side by side for each category
Summary
- A statistical question needs data that varies.
- Mean = sum ÷ count; median = middle of the sorted values (average the two middle ones for an even count).
- Outliers pull the mean but hardly change the median.
- Dot plots and double bar graphs show spread and comparisons; read the scale before concluding.