Try answering the following question based on the expenditure stacked bar chart you saw earlier: Which family has the smallest share of their total expenditure towards healthcare? Was it easy? If not, what visualisation can help answer such questions easily?
Step-by-step solution
| Housing | Food | Education | Transportation | Healthcare | Recreation | |
|---|---|---|---|---|---|---|
| Family A | 1940 | 1700 | 1280 | 1200 | 1770 | 535 |
| Family B | 1750 | 1546 | 1500 | 1280 | 1210 | 0 |
| Family C | 950 | 1700 | 1540 | 1400 | 1300 | 150 |
Idea: A share is a part divided by its own total. In a stacked bar, every family’s total is different, so equal-looking pieces can be very different shares. A chart that makes every total the same size (a pie, or a 100% bar) shows shares directly.
- Healthcare shares: A = 17708425 ≈ 21.0%; B = 12107286 ≈ 16.6%; C = 13007040 ≈ 18.5%. Smallest: Family B.1 mark
- Was it easy? No. From the stacked bar we must estimate each healthcare piece and each whole bar and then divide, because the bars are of different lengths and the pieces start at different places.1 mark
- Better visualisation: a pie chart for each family, or a 100% stacked bar chart, where every family’s bar has the same length (100%) and is split by shares. Then the shortest healthcare piece is the smallest share (see the diagram).1 mark
Answer to write in the exam
Healthcare share: A = 17708425 × 100 = 21.0%
B = 12107286 × 100 = 16.6%; C = 13007040 × 100 = 18.5%
Not easy from a stacked bar: bars have different totals
∴ Family B has the smallest share; a pie chart or 100% stacked bar chart shows shares easily
Common mistakes that cost marks
- Answering Family B only because its healthcare amount (₹1210) is smallest. Shares depend on the totals too; here it happens to agree, but it need not.
- Dividing by the grand total of all families instead of each family’s own total.
- Suggesting a cluster chart, which shows amounts, not shares.
How this can come in the exam
Which chart is best for comparing the share of income each of three families spends on food?
- Cluster column chart
- Stacked bar chart
- 100% stacked bar chart
- Line graph
Show answer
(C) 100% stacked bar chart
A 100% stacked bar makes every family’s total the same length, so the food pieces show the shares directly.
Try one yourself
Family X spends ₹900 of ₹6000 on travel and Family Y spends ₹1000 of ₹8000. Which family spends the larger share on travel?
Show answer
X: 9006000 = 15%; Y: 10008000 = 12.5%. Family X, although it spends less money.
More questions like this
- The average category-wise daily electricity consumption of a house, in kWh, in 2005 and 2025 is shown in the table below. The corresponding stacked bar chart is also shown. Make the corresponding 100% stacked bar chart.
- What do you observe? What do you find interesting in the data/graphs? Discuss with others.
- The 100% stacked bar below compares the proportion of flowers blooming in Fatima’s garden and Naveen’s garden across seasons. Which of the following statements can be inferred from this chart?
(Hint: Find out the blooms per season in each garden if both the gardens had the same total number of blooms over the year. Similarly find out what happens if the totals are very different.) - 1. What does this say about the scope of the stacked bars and 100% stacked bars?
2. Given a stacked bar chart can we make a corresponding 100% stacked bar chart?
3. Given a 100% stacked bar chart can we make a corresponding stacked bar chart?
4. What kind of inferences or comparisons can be made from a stacked bar chart and in a 100% stacked bar chart? - The following chart shows the time spent on different activities in a day by the average Indian. What do you notice? What do you wonder about?