Statistics Definitions Flashcards
Population
Whole set of items that are of interest
Sample
Some subset of the population that is intended to represent the population.
Sampling Unit
Each individual thing in the population that can be sampled.
Sampling frame.
Individually named or numbered to form a list.
Census
Data collected from whole population
Simple Random Sampling
Equal chance of being selected.
+free of bias, cheap, easy
-not suitable if large pop, sampling frame needed
Systematic Sampling
Random Sampling
Chosen at regular interval from order list.
Take every kth element (k=pop size/samp size). Start at random item between 1-k.
+simple, quick, suitable for large pop and sample
-sf needed, sf not random, bias can be intro
Stratified Sampling
Random Sampling
Pop divided into mutually exclusive strata + random sampling from each
(No in stratum/no pop)*sample size
+sample reflects pop structure, proportional rep of groups within pop
-pop can be classified into strata, - of srs are found in selection in stratum
Quota Sampling
Non Random Sampling
Select sample that reflects the characteristics of the whole pop.
+small sample still reflects pop, no sf, quickly, easy, cheap
-intro bias, pop divided into groups=costly + inaccurate, increase scope of study, more expensive, non responses not recorded
Opportunity Sampling
Non random sampling
Sample from people available at time who fit category
+easy, cheap
-not representative sample, dependent on researcher
Qualitative/Categorical Data
Non numerical values
Quantitive Data
Discrete
Continuous
Numerical Values
Only take specific values
Can take decimal places
Reasons for Binomial
Fixed no trials
2 possible outcomes
Fixed probability of success
Trials are independent
Reasons for poison
Events are independent
Singly in space or time
At constant average rate
A U B
A union B
A + B
