Teacher guide — Grade 8, Unit 3: Collecting and recording¶

Time: 3 lessons + project (about 5 periods). Track: A (no-code).

#	Lesson	Time
1	Consent and privacy	40–45 min
2	Tally and frequency	40–45 min
3	A tidy table	40–45 min
P	Unit project: Collect our class data	2 periods

Before you start¶

Materials: Tally sheets, printed consent line, class roll for codes.
Read docs/pedagogy/lesson-anatomy.md and docs/pedagogy/ai-use-policy.md.

If you have no computers / no internet¶

All eight units run on paper, calculators and the blackboard. Computers are optional (spreadsheet or CODAP, https://codap.concord.org); every activity below has a paper version.

Common misconceptions¶

Writing names 'for convenience'. Use codes: even small classes can embarrass or expose people.
Mixing units in a column (minutes and hours).

Differentiation¶

Support: give a partially filled table / sentence starters; pair with a data-steward role.
Stretch: ask "what would change your conclusion?" and "who is missing?"

Answer key (check questions)¶

Lesson 1: Consent and privacy 1. Why do we use codes instead of names?
Answer: To protect privacy and avoid embarrassment. 2. What should a consent statement say?
Answer: Why we collect, how we will use it, and that saying no is fine. 3. Is it ok to publish a table of each student's weight with names?
Answer: No.

Lesson 2: Tally and frequency 1. Tally for 7 is…
Answer: |||| || (one group of five plus two). 2. In a frequency table the counts must add to…
Answer: The total number of students asked. 3. Frequencies: walk 12, bus 5, cycle 3. How many students?
Answer: 20.

Lesson 3: A tidy table 1. Why should every value in travel_minutes use minutes?
Answer: Mixed units can't be compared or averaged. 2. What should one row be in our class table?
Answer: One student (by code). 3. A blank cell means…
Answer: Missing: record it as missing and mention it; don't guess.

Assessment¶

Starter quiz each lesson (3 questions, one recalling the previous lesson); unit quiz in quiz.yml; project marked with the rubric in docs/pedagogy/assessment.md; 2-minute oral check per group.

Alignment¶

Extends the Grade 8 compulsory Maths statistics chapter (pie chart, mean, median, mode) with question-forming, data collection and interpretation.

Answers: practice exercises¶

4 = |||| · 9 = 卌 |||| · 13 = 卌卌 |||.
Must include: who is asking, why, what is recorded (with codes), who sees it, that "no" is fine.
36 students; Maths 12/36 ≈ 33%.
A: 18/30 = 60%; B: 21/42 = 50%. Class A has the bigger share although B has more walkers.
135–139: 1 · 140–144: 3 · 145–149: 3 · 150–154: 2 · 155–159: 4 · 160–164: 2 · 165–169: 2 · 170–174: 1 · total 18.
Example: (A) 8, 06:00 · (B) 7.5, 05:30 · (C) 8, 06:00 (assumed 10 pm to 6 am) · (D) NA, NA. Assumptions: "up at 6" is 6 am; C's sleep is calculated, not reported.
A 0 is a real value and pulls the mean down. Example: 2, 3, 4 and a missing → mean of 2, 3, 4 = 3; with a false 0 the mean becomes 9 ÷ 4 = 2.25.
Yes: the only Rai student who comes by motorbike is identifiable by anyone who knows the class. Remove or combine the ethnicity column (or merge small groups into "other") before sharing; share only what the question needs.
(i) "main mode" column (the mode used for the longest part): simple, one value per cell. (ii) two columns, walk_minutes and bus_minutes: keeps full information. (Or a yes/no column for each mode.)
e.g. codes not names; only the nurse/teacher holds the key; results reported only for groups of ≥ 5; paper destroyed after use; parents' consent.

Real-data exercises: notes¶

R1 With the link as written (Apr–Dec 2015, M ≥ 4, Nepal box) expect ≈ 300 events. On 2026-10-11 the file had 304: 4.0–4.4: 185 · 4.5–4.9: 82 · 5.0–5.4: 26 · 5.5–5.9: 5 · ≥ 6.0: 6 (7.8 on 25 April, 7.3 on 12 May, plus 6.1, 6.3, 6.6, 6.7). Counts change slightly if USGS revises the catalogue; that is fine. Offer the fallback freely.
R2 The station table is wide (one column per year), so it breaks "one column per variable" (year is a variable). Missing years may be blank or marked with a symbol; discuss. Grade 9 Unit 1 tidies exactly this kind of table.
R3 Check consent statements before students start.