AS-Level Maths: Statistics: Ch1: Data Collection Flashcards
What is a ‘Population’?
A Population is the whole set of items that are of Interest.
What is a ‘Census’?
A Census Observes/Measures Every Member of a Population.
What is a ‘Sample’?
A Sample is a Subset of the Population intended to Represent the Population.
Advantages of ‘Census’: (1)
It should give Completely Accurate Results.
Disadvantages of ‘Census’: (3)
-Time Consuming & Expensive.
-Cannot be Used when the Testing Process Destroys the Item.
-Hard to Process Large Quantity of Data.
Advantages of using a ‘Sample’: (3)
-Quick, Cheap & Easy.
-Fewer People have to Respond than in a Census.
-Less Data to Process than in a Census.
Disadvantages of using a ‘Sample’: (2)
-Data may Not be as Accurate as Census.
-The Sample may not be Large enough to Represent Small Sub-Groups of the Population.
The Larger the Sample, the More ___ it is.
Accurate.
The ___ the Sample, the More Accurate it is.
Larger.
Individuals of a Population are known as…
Sampling Units.
Sampling Units are often Numbered to form a ___, Called a..
List, Sampling Frame.
What is a ‘Sampling Frame’?
A Sampling Frame is a List Formed from Sampling Units of a Population that are Numbered.
In Random Sampling, every Member of the Population has…
An Equal Chance of being Selected.
Random Sampling is ___ of the Population. Why?
Representative. Because Every Member of the Population has an Equal Chance of being Selected.
Random Sampling is Representative of the Population. Why?
Because in Random Sampling, Every Member of the Population has an Equal Chance of being Selected.
3 Methods of Random Sampling: (3)
-Simple Random Sampling.
-Systematic Sampling.
-Stratified Sampling.
What is needed to Carry out a Simple Random Sample?
A Sampling Frame, Usually a List of Sampling Units.
What are the 2 Methods to Selecting the Sampling Units from a Sampling Frame? (2)
-RNG
-Lottery Sampling
In both Cases, every Member of the Population is assigned a Number.
How are the Sampling Units Chosen in Systematic Sampling?
They are Chosen in a List, at Regular Intervals.
In Stratified Sampling, the Population is ___ into Groups, and a ___ ___ is Taken from each.
Divided, Random Sample.
What is a ‘Sampling Unit’?
A Sampling Unit is Each Individual thing in the Population that Can be Sampled.
What is ‘Simple Random Sampling’?
Simple Random Sampling is when Every Sampling Unit has an Equal Chance of being Selected.
Method of ‘Simple Random Sampling’:
In a Sample Frame, each Sampling Unit is assigned a Number. Then, using RNG, Sampling Units are Chosen.
Advantages of ‘Simple Random Sampling’: (3)
-Bias Free.
-Easy & Cheap.
-Each Sampling Unit has an Equal Chance of being Chosen.
Disadvantages of ‘Simple Random Sampling’: (2)
-Not Suitable when Population Size is too Large.
-Sampling Frame Needed.
What is ‘Systematic Sampling’?
Systematic Sampling is when Sampling Units are Chosen at Regular Intervals from a List.
Advantages of ‘Systematic Sampling’: (2)
-Quick & Easy.
-Suitable for Large Samples/Populations.
Disadvantages of ‘Systematic Sampling’: (2)
-Sampling Frame Needed.
-Can Introduce Bias if Sampling Frame is Not Random.
What is ‘Stratified Sampling’?
Stratified Sampling is when a Population is Divided into Groups (Strata), & a Simple Random Sample is Carried out in Each Group.
Advantages of ‘Stratified Sampling’: (2)
-Reflects Population Structures.
-Guarantees Proportional Representation of Sub-Groups within the Population.
Disadvantages of ‘Stratified Sampling’: (1)
Population Must be Divided into Strata.
What is ‘Quota Sampling’?
Quota Sampling is when the Population is Divided into Groups According to Characteristic.
A Quota of Sampling Units in each Group is set to try and Reflect the Group’s Proportion in the whole Population.
Advantages of ‘Quota Sampling’: (4)
-Allows Small Sample to still be Representative of Population.
-No Sampling Frame Required.
-Quick, Cheap, Easy.
-Allows for Easy Comparison between different Sub-Groups in Population.
Disadvantages of ‘Quota Sampling’: (3)
-Non-Random Sampling Can Introduce Bias.
-Increasing scope of study Increases Time & Cost.
-Non-Responses are Not Recorded.
What is ‘Opportunity/Convenience Sampling’?
Opportunity/Convenience Sampling is Sample Taken from People who are found & Studied at the same time.
Advantages of ‘Opportunity/Convenience Sampling’: (2)
-Cheap
-Easy
Disadvantages of ‘Opportunity/Convenience Sampling’: (2)
-Unlikely to Provide a Representative Sample.
-Highly Dependent on Individual Researcher.
