Stacked bar charts · 5 marks

Individual project: Do at least one of the following.

(i) Recall the previous day and fill in the approximate time spent lying down, sitting, and standing/moving around, etc. Ask at least 2 of your family members about their day and fill it in. Alternatively, you can choose to track just your own body-state for any one of the weekdays, Saturday, and Sunday. Visualise it using a stacked bar chart. Discuss with your class how you arrived at the estimated time spent in each state.
(ii) Visualise your family’s monthly expenditure using a 100% stacked bar chart.
(a) First, identify the expense categories in your family budget.
(b) Discuss with your family members to decide how you will collect and organise the data.
(c) Collect expense data for at least 3 months.
(d) Represent the data in a 100% stacked bar chart, with each bar showing how the total monthly expenditure is divided across the different categories.
(e) Finally, write your observations and inferences based on the chart.

Answer: A model answer for both: (i) record hours lying down, sitting and standing/moving for yourself and 2 family members (each adding to 24 h) and draw one stacked bar per person; (ii) list expense categories, collect 3 months of expenses, convert each month to percentages of its total and draw one 100% stacked bar per month, then write what you notice.

Step-by-step solution

Idea: For (i), every person’s bar totals 24 hours, so a stacked bar of hours also works as a 100% bar. For (ii), months have different totals, so convert to percentages to compare how the money is divided.

(i) Recall the previous day and fill in the approximate time spent lying down, sitting, and standing/moving around, etc. Ask at least 2 of your family members about their day and fill it in. Alternatively, you can choose to track just your own body-state for any one of the weekdays, Saturday, and Sunday. Visualise it using a stacked bar chart. Discuss with your class how you arrived at the estimated time spent in each state.

Sample data (hours): Me: lying 9, sitting 9, standing/moving 6. Mother: 7, 5, 12. Father: 7, 11, 6. Each row adds to 24 h.1 mark
Draw one bar per person on a 0–24 h scale, with pieces in the same order and colours (top chart in the diagram).1 mark
How the estimates were made: lying = sleep time (bedtime to waking up) plus rest; sitting = school/office hours at a desk, meals, travel, TV and homework; standing/moving = whatever is left of 24 h.½ mark

One stacked bar per person (sample in the diagram)

(ii) Visualise your family’s monthly expenditure using a 100% stacked bar chart.
(a) First, identify the expense categories in your family budget.
(b) Discuss with your family members to decide how you will collect and organise the data.
(c) Collect expense data for at least 3 months.
(d) Represent the data in a 100% stacked bar chart, with each bar showing how the total monthly expenditure is divided across the different categories.
(e) Finally, write your observations and inferences based on the chart.

(a)–(c) Categories: food, rent, transport, education, other. Keep a notebook of bills for 3 months. Sample data (₹):
Month Food Rent Transport Education Other Total
June 12,000 15,000 4,000 6,000 3,000 40,000
July 13,000 15,000 4,500 9,000 3,500 45,000
August 12,500 15,000 4,000 6,000 7,500 45,000
1 mark
(d) Percentages: June: food 12,00040,000 = 30%, rent 37.5%, transport 10%, education 15%, other 7.5%. July (₹45,000): 28.9%, 33.3%, 10%, 20%, 7.8%. August (₹45,000): 27.8%, 33.3%, 8.9%, 13.3%, 16.7%. Draw three bars of equal length (bottom chart).1 mark
(e) Rent is the largest share every month but its share falls when spending rises, since rent is fixed. Education jumps in July (new school year), ‘other’ in August (a festival or repairs). Food stays about 28–30%.½ mark

One 100% bar per month (sample in the diagram) with observations

Answers depend on your own data. The model answer shows (i) one stacked bar of hours per person, each totalling 24 hours, and (ii) one 100% stacked bar per month made by dividing each expense by that month’s total, followed by observations such as ‘rent is the biggest share; education peaks in July’.

Answer to write in the exam

(i)

Me: 9 + 9 + 6 = 24 h; Mother: 7 + 5 + 12 = 24 h; Father: 7 + 11 + 6 = 24 h

One bar per person on a 0–24 h scale, pieces: lying, sitting, moving

Lying = sleep + rest; sitting = school/office, meals, travel; moving = remaining hours

∴ Stacked bar chart drawn

(ii)

Categories: food, rent, transport, education, other

Share = category amountmonth’s total × 100

June: 30%, 37.5%, 10%, 15%, 7.5%

July: 28.9%, 33.3%, 10%, 20%, 7.8%; August: 27.8%, 33.3%, 8.9%, 13.3%, 16.7%

∴ Rent largest; education peaks in July, other in August

Common mistakes that cost marks

Hours for a person that do not add up to 24.
In (ii), drawing bars of different lengths (actual rupees) when a 100% chart is asked for.
Changing the order or colours of categories between bars, which makes comparison hard.

How this can come in the exam

Short answer (2 marks)

A family spent ₹8,000 on food, ₹10,000 on rent and ₹2,000 on other things in a month. Find the percentages for a 100% stacked bar.

Show answer

Total ₹20,000 (½ mark). Food 40%, rent 50%, other 10% (1½ marks).

Try one yourself

Your day: lying 8 h, sitting 11 h, moving 5 h. Where do the pieces of your stacked bar start and end on a 0–24 h scale?