4. Data Handling and Presentation

7 topics1 h

Chapter 4 of NCERT Mathematics for Class 6: Data Handling and Presentation. Four sections — From a question to a table, Pictographs, Bar graphs and Presentation, and its pitfalls. Seven videos, 1 h in all.

Worked answers to the 30 exercise questions in this chapter →

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Part 1

From a question to a table

9 minTurning an argument into a question you can settle with dataNavya is certain cricket is her class's favourite. The count says hockey wins with 8 — and cricket ties basketball at 6, so it is not even second on its own. The most confident person had the least evidence, and the chapter is built that way on purpose.9 min · 12 partsहिंदी9 minTally marks and frequency: organising data so it can be readA tally mark is not a tidier numeral. It is the notation you need when the data is walking past you and will not wait — one stroke, no reading, no crossing out. And the crossing stroke on every fifth is not decoration: it is what lets the record be read later without being counted again.9 min · 12 partsहिंदी

Part 2

Pictographs

10 minPictographs, and why the scale has to be statedFive symbols mean five students on one page and fifty on the next. Nothing in the drawing tells you which — the key does, and it sits outside the picture. Leave it off and a reader still gets an answer: a confident, wrong one.10 min · 12 partsहिंदी

Part 3

Bar graphs

10 minReading a bar graph: what length is standing forA bar graph stops counting objects and starts measuring a length — which is why it carries a thousand million people as easily as three absent students. But it only tells the truth because of two conventions that look like housekeeping, and are not.10 min · 12 partsहिंदी10 minDrawing a bar graph, and choosing a scale that fitsDrawing a bar graph is a division problem wearing a ruler. Once the scale is fixed every height is frequency divided by scale, so the whole procedure has exactly one decision in it — and the chapter's sharpest trap shows what happens when you add the wrong column: 28 instead of 90.10 min · 12 partsहिंदी

Part 4

Presentation, and its pitfalls

10 minWhat makes a data picture clear and worth looking atA table of the seven continental summits is completely accurate and almost useless. Draw the same seven numbers as bars and a shape appears that the table hid entirely — Everest alone at the top, five mountains bunched in the middle, and one far below all of them.10 min · 12 partsहिंदी10 minHow a decorated graph can mislead an honest readerWiden the triangles as you heighten them and the picture quietly claims that taller mountains are broader. Worse: the ink grows as the square, so Everest's triangle covers sixteen times the area of Kosciuszko's for a mountain four times as tall. The defence is not better taste — it is one multiplication.10 min · 12 partsहिंदी

What you will be able to do

  • State what this book means by data, and give an example that is not numbers
  • Record a running count using tally marks, bundling every fifth stroke
  • Read a pictograph correctly by first reading its key
  • Read a named value off a bar graph using the graph's stated scale
  • Set up the two perpendicular reference lines and decide which carries the categories and which the frequencies
  • Explain why a table of numbers is a poor instrument for comparison, using the chapter's own seven-mountain example
  • Define an infographic as a data display with substantial artistic imagery added, and say what it is for

What this chapter assumes you already know

  • Counting a set of objects reliably, and comparing two counts
  • Reading a simple list where each entry pairs a name with a word
  • No prior work on tables, tallies or graphs is assumed
  • Counting in fives, and adding a run of small numbers
  • Comparing whole numbers, and putting a short list in increasing order
  • Reading a two-column table
  • Multiplication of a small whole number by 5 and by 10
  • Halves: half of 10 is 5, and recognising a half of a drawn symbol

It builds directly on Mathematics is the search for patterns and for why they hold.

Where people usually slip up

Sentences students actually say, taken from the notes the videos were made from. Each one is answered on the page of the video it belongs to.

  • "I already know the answer, so collecting is a formality."
  • "Data means numbers."
  • "Any question can be answered by asking people."
  • "More responses is always better."
  • "The list is the answer."
  • "My favourite counts extra because I feel strongly."
  • "Tally marks are just a childish way of writing numbers."
  • "A crossed bundle means five more."