Cover lesson · Design Technology · Year 8 · Intermediate
DCF: Citizenship → Health and well-being
Also assessed, LNF: Numeracy → Statistics and probability → Interpreting data
Name: Class: Date:
What this practises: using technology without harming your body, and reading data accurately. Pupils use body measurements (anthropometric data) to set the adjustment ranges for the chairs, desks and monitors in an invented school computer room, analyse a class log of screen time and breaks, fix 3 badly set up workstations against health guidance, and write the poster text for the room. The numeracy assessed is the range working in Step 2 and the log analysis in Step 3.
Print: this sheet, one per pupil, and the stimulus sheet “The new computer room: body data, guidance and a class log”, one between two. Pupils need a pen, a calculator and a ruler. No computers are needed.
Run: 5 min read the stimulus sheet · 7 min Step 1, percentiles · 12 min Step 2, adjustment ranges · 12 min Step 3, the class log · 10 min Step 4, fix 3 workstations · 7 min Step 5, poster text · 2 min check against the success criteria. Total 55 minutes.
Collect: this sheet. All the answers are on the worked example sheet. The numbers to check first: the desk must adjust from 55 to 70 cm, the top of the screen from 102 to 124 cm above the floor, and 3 pupils in the log broke the break rule. The chair row in Step 2 is already filled in as a model.
A chair that fits one pupil can hurt another. Designers use anthropometric data (measurements of human bodies) to make furniture that adjusts to fit nearly everyone. You will set the ranges for a new computer room, then use health guidance and a class log to make sure pupils use the room in a way that protects their backs, necks, eyes and well-being.
(a) The 95th percentile sitting eye height is 790 mm. Explain in your own words what this tells a designer.
(b) A company offers chairs with one fixed seat height of 41 cm, the 50th percentile knee-to-floor height. Why would this chair be a poor choice for the room?
(c) The brief says the furniture must fit 90% of pupils. Explain why a range from the 5th to the 95th percentile covers 90%. Who is left out, and how could they still be helped?
Use table A on the stimulus sheet. Assume each pupil sets the seat to their own knee-to-floor height. Show your working in mm, then convert to cm (divide by 10).
| Setting | How to work it out | Smallest pupil: 5th percentile (mm) | Largest pupil: 95th percentile (mm) | Adjustment needed (mm) | Range in cm |
|---|---|---|---|---|---|
| Chair seat height | knee-to-floor height | 370 | 450 | 450 − 370 = 80 | 37 to 45 cm (8 cm) |
| Desk height (desk top at elbow height) | knee-to-floor + sitting elbow height | ||||
| Top of screen above the floor (at eye level) | knee-to-floor + sitting eye height |
(b) The mouse must be close enough to use with the elbow by the side. Which percentile of forearm reach should set the furthest the mouse can be from the elbow? Give the value in cm and explain your choice.
(c) The chair the school likes (invented catalogue) has a seat that adjusts from 40 to 50 cm. Compare this with your chair range. Which pupils does it not fit, by how much, and what simple item from the guidance would solve it?
Use log C on the stimulus sheet. Show your working.
| Question | Working and answer |
|---|---|
| Mean total screen time, in minutes and in hours and minutes | |
| Range of total screen time | |
| Median total screen time | |
| Which pupils broke the 50-minute break rule? | |
| What percentage of the 10 pupils is that? |
(b) Check the class representative’s mean of 47.5 minutes. Is the sum right? Then explain why the conclusion “our class keeps the break rule” is misleading, and write a correct conclusion.
(c) One value in the total screen time column is much bigger than the rest. Which is it? Is the mean or the median the fairer “typical” value for this class, and why?
A. Mali has a knee-to-floor height of 390 mm. Her seat is set at 45 cm. Her feet do not reach the floor and the front of the seat presses into the back of her knees.
B. Owain has put his monitor on 2 textbooks, so the top of the screen is 12 cm above his eyes and he tips his head back. The window is directly behind him and he can see it reflected in the screen.
C. Rhodri has his laptop flat on the desk, about 30 cm from his face. He hunches forward to look down at it, his mouse is at the far corner of the desk, and he has worked for 70 minutes without a break.
| Setup | What breaks the guidance (name each problem) | Your fix (give a measurement where you can) |
|---|---|---|
| A. Mali | ||
| B. Owain | ||
| C. Rhodri |
Write 5 short points for a poster by the door. Start each with a verb (Set, Raise, Take). Cover the seat, the desk and keyboard, the screen, glare and breaks. Include at least 2 numbers from your work today, and at least 1 point about balancing screen time with the rest of your life.
Model: 1. Set your seat so your feet are flat on the floor. Too high? Ask for a footrest.