Sampling And LDS Booklet Flashcards
Population
A set of things you are interested in
Census
Measures every member of a population
Parameter
Number that describes the whole population eg mean
Sample
Used to find information about a population
Statistic
Value calculated from sample and used p to estimate a a parameter
Sampling unit
An individual unit from a population eg one person in the uk
Sampling frame
List if all the sampling units
Similarity in census and sample
Both used to find information about a population
Advantages of census and sample
Census = very reliable
Sample = easy to carry out
Disadvantage of census and sample
Sample = not as reliable as census
Census = hard to carry out
2 types of sampling
Random
Non random
3 types of random sampling
Simple
Systematic
Stratified
Simple sampling
Number all items and use random number generator to select sample
Advantages/ disadvantages of Simple sampling
+= easy and cheap for a small sample in a small population
- = not suitable for when population is large
Systematic sampling
Number all items
N = population size/ sample size
Use random number generator from 1-n to select n items
Choose nth item after that
Advantages/ disadvantages of systematic
+ = simple and quick
-= is biased/ sampling frame is needed
Stratified sampling
Population divided into groups
Sample size= number in group / number in population
And do simple sampling in each group
Advantages/ disadvantages of stratified sampling
Advantages = accurate / disadvantages = must be classified into groups
2 types of non sampling methods ( no sampling list )
Opportunity
Quota
Opportunity sampling
Items that are available to be sampled
Advantages/ disadvantages of opportunity
+= easy to carry out /cheap
- = highly dependent on researcher
Quota sampling
Population divided into groups and sample until required number and ignore any repeats
Advantages/ disadvantages of quota
+= quick easy cheap
-= biased / must be divided into groups
Times for large data set
May - October ( 1987 and 2015)
5 uk weather station
Camborne( south )
Hurn
Heathrow
Lemming
Leucahars ( north )
3 overseas weathers stations
- Beijing ( very hit and very cold )
- Jacksonville
- Perth ( opposite weather seasons )
What does n/a mean
Not available
What does tr mean
Trace- less than 0.05 mm of rain
Replace with 0.025
What is cloud cover measured in
Oktas ( 9)
