statistics data collection Flashcards
population
the population is everyone or everything you are interested in
census
if you collect data from the whole population its called a census
sample
if you collect data from part of the population its called a sample
sampling unit
the population broken down into sectors
sampling frame
how you can get a list of the population
simple random sampling method
everyone has equal chance of getting picked
this can be done many ways for example giving everyone in you population a number and then using a random number generator to randomly pick people
pros of random sampling method
-no bias
-efficient and chap if population is small
-every person has equal chance
cons of random sampling methods
- could be not representative of the whole group
-not suitable for a large sample
-need a full sampling frame
systematic sampling method
randomly pick a number one then pick everyone after in a set interval
pros to systematic sampling
-simple and quick
-suitable for a large population
representative of whole population
cons to systematic sampling
-need sampling frame
- bias can happen if sampling frame not random
stratified sampling method
split population into strata’s (groups) to insure each group is proportionally represented as the sample is split in proportional to the population
stratified sampling pros
-sample reflects the proportion structure
-proportionally representative of al the groups in the population
stratified sampling cons
-have to organise population into strata’s
-could suffer from all the con s of the other two as they are often used within this method
quota sampling method
picking people that match your criteria only and selecting them using convenience sampling
pros of quota sampling
-quick and easy
cons of quota sampling
-non random sampling can introduce bias
-can be costly
opportunity/ convenience sampling method
picking people in the most convenient way possible so whoever you come across
opportunity/ convenience sampling pros
-quick and easy
opportunity/ convenience sampling cons
-unlikely to be representative of the whole group
quantitive
uses numbers
qualitive
uses words
continuous
is measured
discrete
can be counted
class boundaries
the maximum and minimum values that belong in each class
midpoint
average of class boundaries
class width
difference between the upper and lower class boundaries
advantages of a census
completely accurate results
disadvantages of a census
time consuming and expensive
advantages of using a sample
less time consuming and expensive then census
less data to process
disadvantages of using a census
data may not be as accurate
sample my exclude small group of population depending on size
what are sampling units
individual units of the population
