Data Collection Flashcards
What is a Census?
A data collection method where the entire populations data is collected.
What are the advantages of a Census?
It’s the most accurate method.
What are the disadvantages of a Census?
It’s time consuming and expensive. It cannot be used if the data collection destroys the product (e.g. food sampling). It can be hard to process a large amount of data.
What is a Sample?
A selection of observations taken from a subset of the population which is used to find out information about the whole population.
What are the advantages of a Sample?
It’s less time consuming and cheaper. It produces fewer data to process. Fewer people have to respond.
What are the disadvantages of a Sample?
It can be influenced by bias. It may not be as accurate as a census. The sample may not be large enough to represent the population.
What are sampling units?
The individual units of the population.
What is a sampling frame?
The sampling units in a list
What is random sampling?
Sampling where everyone in the population has an equal chance of being picked.
What is a simple random sample?
A simple random sample is where a sampling frame is assigned numbers and from this random members are picked out.
What are the two methods of a simple random sample?
A random number generator or lottery, where you assign each thing a number and then randomly decide which ones to choose.
What is a systematic sample?
Where required elements are chosen at intervals on a list.
How do you carry out a systematic sample?
You find out the intervals you will need and then randomly choose a number between the 0 and the first interval. Then go up in intervals until you have the required sample.
What is stratified sampling?
Where the population is divided into strata (groups) and randomly chosen based off them. The proportion should be the same for each.
How do you calculate the sample you take from each stratum in Stratified sampling?
(Size of stratum / Population size) x Sample wanted
What are the advantages of a simple random sample?
Cheap and Easy. Free of Bias. Each member has an equal chance of being picked.
What are the disadvantages of a simple random sample?
Unsuitable for large populations. Requires a sampling frame.
What are the advantages of systematic sampling?
Quick and easy to use. Suitable for large populations.
What are the disadvantages of systematic sampling?
Can introduce bias if the sampling frame isn’t random. Requires a sampling frame.
What are the advantages of stratified sampling?
Reflects the structure of a population. Represents groups of a population within proportion.
What are the disadvantages of stratified sampling?
The population must be in groups. When randomly picking from the groups it suffers from the same disadvantages as simple random sampling.
What is non-random sampling?
Sampling which is not random.
What is quota sampling?
Where a list of required things that reflect the whole population is needed in the sample and you pick those things to be sampled.
What is opportunity sampling?
Where you take the sample from the first people you see.
