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Lesson 10 of 11

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8 min

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Eight ideas, eight checks. The table comes first, so nothing has to be remembered cold.

Eight ways to report a set of numbers without misleading anyone
IdeaHow it goes
The tableEach value once, frequency beside it.
Weighted meanEach mean times its size, added, divided by the sizes added.
WeightsScores times weights, over the weights added. Same number above 0 on every weight, same grade.
Stacked barPieces as segments. The full height is the total.
100% stackedShares only. A count needs a total.
Picking chartsA count, a share or a change decides the chart.
Two storiesHonest charts can leave different impressions.
The reportQuestion, table, average, chart with total, units.

The absences on 20 days add up to 24. What is the mean per day?

  • 4.8, from 24 ÷ 5
  • 24, the total
  • 1.2, from 24 ÷ 20

20 learners averaged 60 and 30 learners averaged 70. What is the mean for all fifty?

  • 66, from the two totals over fifty learners
  • 65, halfway between the two means
  • 70, because the bigger group wins

Scores 70, 85, 95 have weights 1, 2, 3 and give 87.5. What if every weight is multiplied by 10?

  • The grade is ten times bigger
  • Impossible, until the weights total 100
  • 87.5 again, because the shape is the same

A stacked bar reaches 100 quintals. It is cut into paddy 40, ragi 25, pulses 35. What does the full height show?

  • The paddy, because it is at the bottom
  • The season's total
  • The tallest crop

Two seasons have identical 100% stacked bars. What can you read from the bars alone?

  • The seasons made equal amounts
  • One season made twice the other
  • Each crop had the same share of its own season

Did the bus take longer on each day of the week? Which chart answers it?

  • A pie chart
  • A line graph, because the days have an order
  • A 100% stacked bar

A bar graph shows every crop doubled. A 100% bar shows the same shares. Which impression does the 100% bar give?

  • That the mix did not change
  • That the farm doubled
  • That paddy overtook ragi

A note says: "Season 2 gave 80. Season 1 gave 40." What does it need to be clear?

  • A pie chart of the two seasons
  • A bigger number for season 2
  • A unit, like quintals

The Class 9 syllabus also covers statistics. The five parts of the report will carry you into it.

Reveal every answer to finish this lesson.

That is the end of this subject for Class 9

Nicely done. There is more waiting at this same level — pick whichever you like.