Sampling Methods

Random Sample

Each subject has the same chance of being selected

Simple Random Sample

Each sample of size n is equally likeley

Systematic Sampling

Take every kth subject after some random starting point

Stratified sampling

subdivide the population into several large subgroups and conduct a SRS

Cluster Sampling

Subdivide the population into many small clusters, then randomly select some of the clusters and use all of the subjects within each selected cluster

Convenience Sampling

Use whichever subjects are easiest to get

Population

everyone we care about

Experimental Design

How we aquire the sample, how we test treatments on sample

descriptive statistics

self-referential about sample

parameter

a measure of some characteristic of the population

statistic

measure of some characteristic of the sample

census

a measure of everyone

generalize and cause/effect

What can we infer with random sampling and random assignment?

cause/effect

What can we infer with non-random sampling and random assignment?

Generalize

What can we infer with random sampling and non-random assignment?

Observation

What can we infer with non-random sampling and non-random assignment?

q, n, up, 1, 2

How to find Quantiles: 1. Take __ * __ 2. If it is not an integer, then round __. If it is an integer, i, then (x(i) + x(i + _))/__.

median, quartiles, iqr, 1.5*iqr, 3*iqr, x.25-L1, x.75+L1, x.25-L2, x.75+L2, a1, a3, 

Boxplot

1. Find the _______ and both _________. 

2. Find the ___.

3. Find L1 = ________ and L2 = ______. 

4. Find inner fences: f1 = ______ and f3 = ______. and outer fences: F1 = ______ and F3 = _____. 

5. __ is the smallest value in the dataset greater than or equal to f1, and __ is the largest value less than or equal to f3. 

P(A)*P(B)

Probability of A intersect B equals this if A and B are independent.