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TA Focus

Cold Call

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Messages · Dr M. Calder now
Don't drown 🦺
Before you set foot on the riverbank — risk plan + sampling strategy. No exceptions. Today's the day.

Lesson 18 — PGFI

Risk & Sampling

"How do we stay safe — and pick fair sites?"

🦺
+
🎯

Spot the hazards · Pick fair sites

PGFI Obj 3 evidence by the end · 50 minutes

FAB 4 · Arrival

FAB 4 Arrival – Recall from last lesson

Whiteboards. 4 minutes. Easy ones — straight from last lesson's river parts. Q4 leads into today.

1. Recall

Where does a river start? (one word)

Source.

2. Recall

Where does a river end? (one word)

Mouth.

3. Recall

What do we call a smaller river that joins a bigger one?

A tributary.

4. Lead-in 🔬

You're standing on a riverbank with a clipboard. Name 1 thing that could go wrong.

Many: slipping, falling in, dropping kit, getting cold, weather turning… anything sensible.

Starter

How risky is each one?

1 on the bank 2 shallow edge 3 middle of channel

Tap each card to reveal the verdict.

1 · LOW
📝
Stand on the bank with a clipboard.
No water contact, dry ground. Worst case: drop your pen.
2 · MEDIUM
🥾
Step into the shallow edge with a metre stick.
Wet rocks slip, water is cold. Wellies, buddy, knee-deep max.
3 · HIGH
⚠️
Wade to the middle after heavy rain.
Don't. Current sweeps adults off their feet. Measure from the bank — or skip that day.
I Do · 1 of 2

What's in a risk row?

4 things, in this order:

⚠️
Hazard
slipping
👥
Who?
pupils & staff
📊
Level
MEDIUM
🦺
Control
wellies + buddy

"Slipping could happen to pupils. Risk: MEDIUM. We will wear wellies + buddy holds hand."

✗
"Be careful" isn't a control. A control says what you'll do.
✗
Match the consequence to the actual hazard. Paper cut ≠ death.
We Do · 1

We Do: Fill in OUR first risk row — together

As a class: Hazard = slipping on wet rocks. Click each yellow box to type — class agrees, then we lock it in.

" Slipping on wet rocks could happen to . We think this is risk because . To control this, we will and ."

💡 Suggestions: who = pupils, staff, public · risk = MEDIUM (likely + can twist an ankle / fall) · controls = wellies, stay back from edge, buddy holds hand, keep depth below knee.

🌟 Aspire — second hazard (optional): Try one for cold water / hypothermia using the same stem. Who is most at risk if it's a winter day?
I Do · 2 of 2

How do we pick fair sites?

3 strategies. Same river. 6 sampling points each. Tap each card to see what each gives us.

🎲

Random

picked by chance

Site ASite B

Best for: removing bias.

Watch out: can cluster by chance.

📏

Systematic ⭐

same gap each time

Site ASite B

Best for: showing change over distance.

⭐ Best fit for OUR aim.

🎯

Stratified

split into zones

Upper Middle Lower

Best for: very different zones (e.g. moor → urban).

We Do · 2

We Do: Match Scenario to Strategy

Click a question, then click the method that answers it. Score: 0/6

Investigation scenario

"We want to show how the river changes over distance, every 200m for 1km."
"We've got 6 sites and want to be sure we're not biased by picking 'nice-looking' bits."
"The river has 3 very different zones — upper, middle & lower — and we need data from each."
"Same gap each time so we can plot a smooth graph of width vs distance."
"We want a small pilot study — pick 5 spots out of a hat to check our method works."
"Land use changes from moorland → farmland → urban — we need samples from each band."

Best strategy

Stratified — split into upper/middle/lower zones, sample each.
Systematic — same gap each measurement (e.g. every 100m).
Random — pick by chance to remove "I-like-this-spot" bias.
Stratified — split by land-use band, sample each.
Systematic — every 200m gives even coverage for distance graphs.
Random — names from a hat / random number generator.
👆 Click a scenario on the left, then the strategy on the right.
We Do · 3

Spot the 3 Mistakes

A pupil wrote this risk & sampling plan. 3 things are wrong. Click the phrases you think are wrong.
1
2
3
One hazard is slipping on wet rocks. To control this we will tell pupils to be careful. Another hazard is cold water causing hypothermia, controlled by wearing waterproofs and limiting time in the water. For sampling we will use a random method by picking spots that look good, and we will measure depth at one point in the middle of each site.
✅ Correct version: "To control slipping we will wear wellies, stay 1m back unless measuring, buddy holds hand, depth below knee. We will use systematic sampling — every 200m for 1km to show change over distance. Depth will be measured at 5 points across the width and averaged at each site."
Team Task · 8 min

📋 Team Brief — 8 minutes

One printed Brief per team. Photo it at the end = evidence.

⚠️ 1
Risk rows
Fill in 4. Hazard · Who · Level · Control.
🎯 2
Sampling
Tick one. Justify in 2 lines.
📊 3
★ Recording sheet
Sketch the table you'll fill next lesson.
Sample risk row: Cold water · pupils & staff · MEDIUM · waterproofs + warm drinks + watch for shivering.
Sample sampling choice: Systematic, every 200m — best for showing change downstream.
🏆 Final Buzzer · 6 Qs

🏆 Final Buzzer Round

6 questions to settle it. Score carries from L16 — Sage may have ground to make up. First team to BUZZ answers. Wrong / pass = the other team can steal.
QUESTION 1 / 6
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Click a team's BUZZ button to claim the question.