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Sampling and bias

Sampling and bias for Functional Skills Engineering: what it means, how to set the working out, and the questions it is asked in.
  • Functional Skills
  • Engineering
  • Spec G18
  • 9 min read
  • 6 revision boxes

Introduction

2 boxes
2 min read

What is sampling and bias?

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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.
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.
5 rows

The sampling and bias reference table

Practise the routine version until it is automatic, then move to the multi-step questions.
Worth knowing: 34×25\frac{3}{4} \times \frac{2}{5}.
Term
Meaning
Example
Row 1 column 1
Row 1 column 2
≈160\approx 160
Row 2 column 1
Row 2 column 2
a2+b2=c2a^2 + b^2 = c^2
Row 3 column 1
Row 3 column 2
x2+5x+6=0x^2 + 5x + 6 = 0
Row 4 column 1
Row 4 column 2
a2+b2=c2a^2 + b^2 = c^2

Learning

2 boxes
3 steps

How to work with sampling and bias

The examiner marks the working, so a correct answer with no method still drops marks.
Worth knowing: 49=7\sqrt{49} = 7.
  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: x2+5x+6=0x^2 + 5x + 6 = 0.
Answer: 34×25\frac{3}{4} \times \frac{2}{5}
2 rules

Key facts: Sampling and bias

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

  • 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.
    a2+b2=c2a^2 + b^2 = c^2

  • Rule 3

    How sampling and bias behaves in the 3rd of the cases the specification names.
    49=7\sqrt{49} = 7

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Examples

2 boxes
4 marks · worked

Worked example: 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.
4 marks · worked

Practice question 6: a2+b2=c2a^2 + b^2 = c^2

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: 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 Functional Skills Engineering paper?
Yes — it sits in the Programming strand.