6.1.2

Statistics Key Terms

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Statistics Key Terms

Statistics is about estimating information about the whole group by using a smaller group.

Population and sample

Population and sample

  • A whole group is called a population and a smaller group within the population is called a sample.
Sample needs to be representative

Sample needs to be representative

  • When choosing a sample it is important for it to be representative of the whole population so that measurements we take in the sample can be used as estimates for the population.
  • To be representative the sample needs to be big enough to be reliable, and the sample should be random so that every member of the population is equally likely to be chosen.
Random sample

Random sample

  • To choose a random sample you can assign a number to each member of the population then use a computer or a random number table or pick numbers out of a hat to choose a random selection of numbers.
  • Pick the members corresponding to these numbers.
Biased sample

Biased sample

  • A biased sample is one that doesn’t represent the whole population.
  • To assess whether a sample is biased think whether any groups of people would be excluded from the sample (e.g. based on gender, age, different interests or habits).
  • A small sample is also likely to be biased.

Types of Data

Primary vs secondary

Primary vs secondary

  • Primary data is data that you have collected yourself.
  • Data from any other source (e.g. from a book or the internet) is secondary data.
Qualitative vs quantitative

Qualitative vs quantitative

  • Qualitative data is descriptive or categorical and uses words rather than numbers (e.g. colours, names).
  • Quantitative data is measured in numbers and represents quantities (e.g. heights, shoe size).
Discrete vs continuous

Discrete vs continuous

  • Quantitative data is discrete if the numbers can only take certain values (e.g. only whole numbers).
  • It is continuous if the numbers can take any value.

Capture-Recapture Method

A capture-recapture method can be used to estimate the population size from a sample.

Process

Process

  • A sample is captured, tagged and released.
  • Later another sample is taken and the number of tagged members is noted.
  • Using the assumption that the proportion of tagged members in the population is the same as the proportion in the sample you can then estimate the population.
Example

Example

  • A biologist captures 15 turtles from a lake and marks their shells with paint.
  • The next week they capture 20 turtles and find 5 have their shells marked.
    • 520 = 15N where N is the population size so the estimate is N = 60.
Jump to other topics
1

Number

1.1

Using Numbers

1.2

Fractions, Decimals & Percentages

1.3

Powers & Roots

1.4

Accuracy

2

Algebra

2.1

Introduction to Algebra

2.2

Manipulating Algebra

2.3

Proofs & Functions

2.4

Straight Line Graphs

2.5

Common Graphs

2.6

Transformations & Tangents

2.7

Properties of Graphs

2.8

Solving Equations

2.9

Inequalities

2.10

Sequences

3

Ratio

4

Geometry

4.1

Introduction to Geometry

4.2

Triangles & Quadrilaterals

4.3

Transformations

4.4

Circle Basics

4.5

Circle Theorems

4.6

Measurements & Units

4.7

Calculating Area

4.8

Triangle Formulae

4.9

3D Shapes

4.10

Vectors

5

Probability

6

Statistics

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