Summary STK 110 Chapter 7 Notes (sampling)

Sampling and Sampling Distributions
Chapter 7
Sampling from Finite 3. Cluster sampling
Population
Simple Random Sample of size n from
finite population of size N = sample
selected such that each possible
sample of size n has same probability
of being selected. (use excel RAND
function) read textbook
Sampling from Infinite
Population
Sample selected such that following
conditions = satisfied:
(1) Each element selected comes from
same population;
(2) Each element = selected
independently.
Parameter
Read textbook E.g. Acc 2 Census 2011 data, average
Types age = 25 yr - taking in2 account ALL
people in SA
1. Systematic random sampling
▪ FIXED value.
methods
▪ Parameter.
▪ Symbol is 𝜇.
Point Estimate
Value of sample statistic = used 2
estimate value of corresponding
population parameter.
e.g. Take representative sample -
2. Stratified random sampling average age = 22.6 years = point
estimate of overall average age
▪ Sample statistic.
▪ Symbol is 𝑥.ҧ
▪ A variable.
Estimator:
▪ Sample statistic used estimate
population parameter.
▪ Examples: 𝑥ҧ & s
Estimate:
▪ calculated value of sample statistic
used estimate population
parameter.