Edexcel AS Maths - Statistics (Chp. 1)

Flashcards for AS Applied Chapter 1 (Statistics - Data collection)

Population

The whole set of items that are of interest in statistics.

Census

An observation or measurement of every member of a population.

Sample

A selection of observations taken from a subset of the population.

Sampling Units

Individual units of a population.

Sampling Frame

A list formed by naming or numbering the sampling units of a population.

Simple Random Sample

A sample where every sample of size n has an equal chance of being selected.

Systematic Sampling

A method where required elements are chosen at regular intervals from an ordered list.

Stratified Sampling

A sampling method where the population is divided into mutually exclusive strata and a random sample is taken from each.

Quota Sampling

A sampling method where an interviewer selects a sample that reflects the characteristics of the whole population.

Opportunity Sampling

A method of sampling where participants are selected based on their availability and fit for the study criteria.

Quantitative Variables

Variables associated with numerical observations.

Qualitative Variables

Variables associated with non-numerical observations.

Continuous Variable

A variable that can take any value within a given range.

Discrete Variable

A variable that can take only specific values within a given range.

Grouped Frequency Table

A table that presents data in groups or classes without showing specific data values.

Class Boundaries

The maximum and minimum values that belong in each class of a grouped frequency table.

Midpoint

The average of the class boundaries in a grouped frequency table.

Class Width

The difference between the upper and lower class boundaries.

Census (Advantages)

It should give a completely accurate result

Census (Disadvantages)

• Time consuming and expensive

• Cannot be used when the testing process destroys the item

• Hard to process large quantity of data

Sample (Advantages)

• Less time consuming and expensive than a census

• Fewer people have to respond

• Less data to process than in a census

Sample (Disadvantages)

• The data may not be as accurate

• The sample may not be large enough to give information about small subgroups of the population

Types of Random Sampling (3)

• Simple random sampling

• Systematic sampling

• Stratified sampling

Simple Random sampling (Advantages)

• Free of bias

• Easy and cheap to implement for small populations and small samples

• Each sampling unit has a known and equal chance of selection

Simple Random Sampling (Disadvantages)

• Not suitable when the population size or the sample size is large

• A sampling frame is needed

Systematic sampling (Advantages)

• Simple and quick to use

• Suitable for large samples and large populations

Systematic sampling (Disdvantages)

• A sampling frame is needed

• It can introduce bias if the sampling frame is not random

Stratified sampling (Advantages)

• Sample accurately reflects the population structure

• Guarantees proportional representation of groups within a population

Stratified sampling (Disadvantages)

• Population must be clearly classified into distinct strata

• Selection within each stratum suffers from the same disadvantages as simple random sampling

Types of Non-random Sampling (2)

• Quota sampling

• Opportunity sampling

Quota sampling (Advantages)

• Allows a small sample to still be representative of the population

• No sampling frame required

• Quick, easy and inexpensive

• Allows for easy comparison between different groups within a population

Quota sampling (Disadvantages)

• Non-random sampling can introduce bias

• Population must be divided into groups, which can be costly or inaccurate

• Increasing scope of study increases number of groups, which adds time and expense

• Non-responses are not recorded as such

Opportunity sampling (Advantages)

• Easy to carry out

• Inexpensive

Opportunity sampling (Disadvantages)

• Unlikely to provide a representative sample

• Highly dependent on individual researcher