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 A Level Combined Science OCR Higher paper?

Yes — it sits in the Programming strand.

Sampling and bias

Sampling and bias for A Level Combined Science OCR Higher: what it means, how to set the working out, and the questions it is asked in.

A Level
OCR
Combined Science
Higher
Spec A8 · A1
10 min read
10 revision boxes

Introduction

2 boxes

1 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.

2 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.

Term	Meaning	Example	Common slip
Row 1 column 1	Row 1 column 2	$\frac{3}{4} \times \frac{2}{5}$	Row 1 column 4
Row 2 column 1	Row 2 column 2	$x^2 + 5x + 6 = 0$	Row 2 column 4
Row 3 column 1	Row 3 column 2	$\sqrt{49} = 7$	Row 3 column 4
Row 4 column 1	Row 4 column 2	$\times 10$ moves every digit one column left	Row 4 column 4

Learning

6 boxes

3 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:

\frac{3}{4} \times \frac{2}{5}

Read the question and write down what is being asked for.
Set out the working for sampling and bias in the order the method gives.
Substitute the values and simplify.
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:

a^2 + b^2 = c^2

Answer:

x^2 + 5x + 6 = 0

3 rules

Key facts: Sampling and bias

The examiner marks the working, so a correct answer with no method still drops marks.

Worth knowing:

\sqrt{49} = 7

Rule 1
How sampling and bias behaves in the 1st of the cases the specification names.
$\sqrt{49} = 7$
Rule 2
How sampling and bias behaves in the 2nd of the cases the specification names.
$\approx 160$

5 steps

How to work with sampling and bias

Practise the routine version until it is automatic, then move to the multi-step questions.

Worth knowing:

\frac{3}{4} \times \frac{2}{5}

Read the question and write down what is being asked for.
Set out the working for sampling and bias in the order the method gives.
Substitute the values and simplify.

Start from the definition and substitute the numbers the question gives you.

Simplify one line at a time:

\sqrt{49} = 7

Answer:

\sqrt{49} = 7

2 rules

Key facts: Sampling and bias

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.

Rule 1
How sampling and bias behaves in the 1st of the cases the specification names.
$\times 10$ moves every digit one column left
Rule 2
How sampling and bias behaves in the 2nd of the cases the specification names.
$\frac{3}{4} \times \frac{2}{5}$

3 steps

How to work with sampling and bias

This idea appears again in the higher-mark questions, so it is worth over-learning.

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:

\approx 160

Read the question and write down what is being asked for.
Set out the working for sampling and bias in the order the method gives.
Substitute the values and simplify.

Start from the definition and substitute the numbers the question gives you.

Simplify one line at a time:

\frac{3}{4} \times \frac{2}{5}

Answer:

\frac{3}{4} \times \frac{2}{5}

3 rules

Key facts: Sampling and bias

The examiner marks the working, so a correct answer with no method still drops marks.

Worth knowing:

\times 10

moves every digit one column left.

Rule 1
How sampling and bias behaves in the 1st of the cases the specification names.
$\sqrt{49} = 7$
Rule 2
How sampling and bias behaves in the 2nd of the cases the specification names.
$\times 10$ moves every digit one column left
Rule 3
How sampling and bias behaves in the 3rd of the cases the specification names.
$x^2 + 5x + 6 = 0$

20 minutes

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Examples

2 boxes

1 marks · worked

Worked example: sampling and bias

The specification wording is precise here, and the mark scheme follows that wording exactly.

4 marks · worked

Practice question 10: $x^2 + 5x + 6 = 0$

This idea appears again in the higher-mark questions, so it is worth over-learning.

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.

Practice bank

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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 A Level Combined Science OCR Higher paper?: Yes — it sits in the Programming strand.

Sampling and bias

What is sampling and bias?

The sampling and bias reference table

How to work with sampling and bias

Key facts: Sampling and bias

How to work with sampling and bias

Key facts: Sampling and bias

How to work with sampling and bias

Key facts: Sampling and bias

Get your predicted grade

Worked example: sampling and bias

Practice question 10: x2+5x+6=0x^2 + 5x + 6 = 0x2+5x+6=0

Thousands of revision questions

Common questions

Practice question 10: $x^2 + 5x + 6 = 0$