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Sampling and bias

Sampling and bias for Access to HE Geography: what it means, how to set the working out, and the questions it is asked in.
  • Access to HE
  • Geography
  • Spec A12 · A4
  • 10 min read
  • 7 revision boxes

Introduction

2 boxes
2 min read

What is sampling and bias?

Listen to this box

Transcript

A short spoken summary of sampling and bias and where it is used.

A spoken walk-through of sampling and bias before you read the notes.
Practise the routine version until it is automatic, then move to the multi-step questions.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.
3 rows

The sampling and bias reference table

Sketch the shape even when the question does not ask for one — it makes the next step obvious.
The layout below is the one the mark scheme expects.

Diagram showing sampling and bias laid out step by step

The same idea drawn out, so the method is visible.
Worth knowing: 34×25\frac{3}{4} \times \frac{2}{5}.
Term
Meaning
Example
Common slip
Marks
Row 1 column 1
Row 1 column 2
a2+b2=c2a^2 + b^2 = c^2
Row 1 column 4
Row 1 column 5
Row 2 column 1
Row 2 column 2
a2+b2=c2a^2 + b^2 = c^2
Row 2 column 4
Row 2 column 5
Row 3 column 1
Row 3 column 2
x2+5x+6=0x^2 + 5x + 6 = 0
Row 3 column 4
Row 3 column 5
Row 4 column 1
Row 4 column 2
49=7\sqrt{49} = 7
Row 4 column 4
Row 4 column 5

Learning

3 boxes
4 steps

How to work with sampling and bias

This idea appears again in the higher-mark questions, so it is worth over-learning.
Worth knowing: ×10\times 10 moves every digit one column left.
  1. Read the question and write down what is being asked for.
  2. Set out the working for sampling and bias in the order the method gives.
  3. Substitute the values and simplify.
  4. Check the answer against an estimate before writing it down.
Start from the definition and substitute the numbers the question gives you.
Simplify one line at a time: ×10\times 10 moves every digit one column left.
Answer: ≈160\approx 160
2 rules

Key facts: Sampling and bias

The examiner marks the working, so a correct answer with no method still drops marks.
The layout below is the one the mark scheme expects.

Diagram showing sampling and bias laid out step by step

The same idea drawn out, so the method is visible.
Worth knowing: 34×25\frac{3}{4} \times \frac{2}{5}.

  • Rule 1

    How sampling and bias behaves in the 1st of the cases the specification names.
    34×25\frac{3}{4} \times \frac{2}{5}

  • Rule 2

    How sampling and bias behaves in the 2nd of the cases the specification names.
    49=7\sqrt{49} = 7

  • Rule 3

    How sampling and bias behaves in the 3rd of the cases the specification names.
    ≈160\approx 160
4 steps

How to work with sampling and bias

Practise the routine version until it is automatic, then move to the multi-step questions.
The layout below is the one the mark scheme expects.

Diagram showing sampling and bias laid out step by step

The same idea drawn out, so the method is visible.
  1. Read the question and write down what is being asked for.
  2. Set out the working for sampling and bias in the order the method gives.
  3. Substitute the values and simplify.
  4. Check the answer against an estimate before writing it down.
Start from the definition and substitute the numbers the question gives you.
Simplify one line at a time: 34×25\frac{3}{4} \times \frac{2}{5}.
Answer: a2+b2=c2a^2 + b^2 = c^2

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Examples

2 boxes
4 marks · worked

Worked example: sampling and bias

Check the answer against an estimate before you move on, so a place-value slip is caught here.
Worth knowing: ≈160\approx 160.
2 marks · worked

Practice question 7: x2+5x+6=0x^2 + 5x + 6 = 0

Work through the method one line at a time and write down what changes at each step.
Worth knowing: x2+5x+6=0x^2 + 5x + 6 = 0.

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Common questions

How many marks is sampling and bias usually worth?
Between one and four, depending on how many steps the question asks for.
Is this on the Access to HE Geography paper?
Yes — it sits in the Programming strand.