Collecting And Interpreting Data Flashcards
What is a population?
A population is the whole set of items that are of interest
What is a sample?
A sample is some subset of the population intended to represent the population
What is a sampling unit?
Each individual in the population that can be sampled is a sampling unit
What is a sampling frame?
Sampling units of a population can be individually named or numbered to form a list called the sampling frame
What is a census?
Data collected from every sampling unit is known as a census
What are the advantages and disadvantages of a census?
Advantage: It should give completely accurate results
Disadvantage: Time consuming, expensive, impossible if testing involves destruction, lots of data to process
What are the advantages and disadvantages of a sample?
Advantages: Quick, Cheap, Less data to process
Disadvantages: Inaccurate, Miss out small sub groups
How do you carry out simple random sampling?
Every sample has an equal chance of being picked.
In sampling frame, each item assigned identifying number and a random number generator or “lottery sampling” is used to pick specific sampling units
What are the advantages and disadvantages of simple random sampling?
Advantages: Unbiased, Easy, Cheap, Equal Chance of Selection
Disadvantages: Impossible with large population, Sampling Frame needed
How to carry out systematic sampling?
Required elements are chosen at regular intervals in ordered list. Every kth elements where
k = pop size///samp size
Starting at a random item between 1 and k
What are the advantages and disadvantages of systematic sampling?
Advantages: Simple, Quick, Can do large samples
Disadvantages: Sampling frame needed, Bias if frame is not random
How to carry out stratified sampling?
Population divided into groups (strata) and simple random sampling occurs within them. Same proportion sampled from each strata:
(Samp size///Pop size) x Strata Size
Used when sample is large and population naturally falls into groups
What are the advantages and disadvantages of stratified sampling?
Advantages: Reflects population structure, Proportional representation of strata in population
Disadvantages: Population must be in strata, Same disadvantages as simple random sampling
How to carry out quota sampling?
Divide population into groups according to characteristics of interest to reflect population proportion. Interviewer selects the sampling units
Proportion of population x Sample Size = Sampling units of a characteristic selected
What are the advantages and disadvantages of quota sampling?
Advantages: Small sample represents population, No sampling frame, Quick, Easy, Cheap, Easy comparison
Disadvantages: Possible bias, Costly or inaccurate to make groups, More groups is more expense, Non-response not recorded
How to carry out opportunity sampling?
Sample taken from people who are available at the time, who meet criteria
What are the advantages and disadvantages of opportunity sampling?
Advantages: Easy, Cheap
Disadvantages: Unlikely to be representative sample, Dependent on researcher (bias)
What does x bar mean?
X bar is the mean of the values in the variable ‘x’
What are measures of location? Examples?
Measures of location are single values which describe a position in a data set (Maximum, Minimum, Quartile, Percentile)
What are the measures of central tendency? Examples?
Within the measures of location, you have the measures of central tendency which are to do with the where the centre of data is (Mean, Medium, Mode)
What are the measures of spread? Examples?
There are measures of spread which are to do with how data is spread out (Range, IQR, Variance, Standard Variation)
What is the equation for x bar?
X bar = Total of X/Number of X values
What is the x bar for a frequency table?
X bar = (Frequency***X)///Frequency
What is the equation for x bar of grouped frequency?
X bar = (Average Frequency***X)///Frequency
