100% stacked bar charts · 4 marks

The smart watch data of 5 people was tracked from Monday to Friday. The recorded data tells us how many hours each person spent lying down, sitting, and standing or moving around, etc., as shown in the following table.

(i) How much time does Sahana spend per day in each of these body-states? Make a reasonable guess and fill her row in the table.
(ii) Guess what activity or work Julie could be engaged in based on the data. Find out what your classmates’ guesses are.
(iii) Complete the chart below based on the tabular data.

Answer: (i) A reasonable guess for Sahana: lying down 9 h, sitting 10 h, standing/moving 5 h (total 24 h). (ii) Julie sits 10 h and moves only 6 h: an office worker (for example, a bank clerk or a software engineer) or a driver. (iii) Convert each row to percentages of 24 h and draw the bars (Sahana: 38%, 42%, 21%).

Step-by-step solution

Given: Average number of hours spent per day (Monday – Friday) lying down, sitting, and standing or moving around, etc., of 5 people

	Lying down	Sitting	Standing or Moving around etc.
Pavani (Patient)	20	3	1
Raghu (Nurse)	7	4	13
Zakir (Teacher)	8	6	10
Sahana (Student)
Julie (___________)	8	10	6

Idea: Each row adds up to 24 hours (one day), so each person’s bar in the chart is that row’s hours as percentages of 24.

(i) How much time does Sahana spend per day in each of these body-states? Make a reasonable guess and fill her row in the table.

A student sleeps about 8–9 h (lying down), sits in class and at homework about 9–10 h, and spends the rest standing, walking or playing. A reasonable guess: lying down 9 h, sitting 10 h, standing/moving 5 h, which adds up to 24 h. (Other guesses are fine if they total 24 h and fit a student.)1 mark

For example: 9 h, 10 h, 5 h

(ii) Guess what activity or work Julie could be engaged in based on the data. Find out what your classmates’ guesses are.

Julie sits for 10 h (much more than the nurse or teacher) and stands/moves only 6 h, with normal sleep (8 h). This fits a desk job: an office worker, bank clerk, software engineer, accountant, or a job like a bus or taxi driver. Classmates’ guesses will vary; any sitting-heavy job is reasonable.1 mark

A sitting-heavy job, e.g. office worker or driver

(iii) Complete the chart below based on the tabular data.

Divide each value by 24 and multiply by 100. Pavani: 83%, 13%, 4%. Raghu: 29%, 17%, 54%. Zakir: 33%, 25%, 42%.1 mark
Sahana (9, 10, 5): 37.5%, 41.7%, 20.8%. Julie: 33%, 42%, 25%. Draw each bar to these lengths (diagram). Since every total is 24 h, this chart is both a stacked and a 100% stacked bar chart.1 mark

Bars drawn with the percentages shown

(i) For example, Sahana: lying down 9 h, sitting 10 h, standing/moving 5 h. (ii) Julie probably has a desk job (office worker, bank clerk, software engineer) or drives for a living. (iii) Each bar is the row’s hours as a percentage of 24 h, as drawn.

Check: Every row sums to 24: 20 + 3 + 1, 7 + 4 + 13, 8 + 6 + 10, 9 + 10 + 5, 8 + 10 + 6 ✓.

Answer to write in the exam

(i)

Lying down (sleep) ≈ 9 h

Sitting (school + homework) ≈ 10 h

Standing/moving ≈ 24 − 9 − 10 = 5 h

∴ Sahana: 9, 10, 5 (total 24 h)

(ii)

Julie: sitting 10 h (highest), moving 6 h, lying 8 h

∴ Likely a desk job, e.g. office worker, or a driver

(iii)

Share = hours24 × 100

Pavani 83%, 13%, 4%; Raghu 29%, 17%, 54%; Zakir 33%, 25%, 42%

Sahana 38%, 42%, 21%; Julie 33%, 42%, 25%

∴ Chart completed as drawn

Common mistakes that cost marks

Filling Sahana’s row with numbers that do not add up to 24 hours.
Dividing by 12 or by the largest value instead of by 24 when finding percentages.
Guessing a very active job for Julie, although she sits most of her waking hours.

How this can come in the exam

MCQ (1 mark)

A person spends 6 hours a day standing or moving. In a 100% stacked bar of the day, this piece is

Show answer

(C) 25%
624 × 100 = 25%.

Try one yourself

A shopkeeper lies down 7 h, sits 5 h and stands/moves 12 h a day. Find the percentages for his bar.