1. SAMPLES Probability Samples Non probability samples
Are Samples that does
not obey the probability
rules specific characteristics
and quality are hosen according
to some specific standards
assumed by the researcher
and does not obey probability
Rules.
Probability Samples
Randomly simple sample.
Stratified random samples.
Systematic random sample.
Groups sample.
Area sample.

2. Random Samples They divided into: Randomly simple sample
Are sample which each individual of the society of research has the same chance in being chosen in the sample.
They divided into:
Randomly simple sample
Are the one chosen so that every individual of the society individual has equivalent chance in being chosen and this process is unbiased
Stratified random samples
It is represented for all category, classes, and area in the society needed to be measured. It is done by choosing individual from each area ( a-b-c-d ) or from categories or classes in a precise percentage.
Every individual is chosen in a randomly way from these categories to increase the probability of representing each one of these groups in the chosen sample.

3. Systematic random sample
Are chosen by dividing a number of society individuals on sample individual and the result is called “ survey range ” .
Sample range = 100/10 = these number 2 ,12 ,22 ,32 ect…core chosen
It is used in investigation of opinion in air planes passengers, movies watcher, supermarkets ….ect.
Groups sample:
it is done by choosing a sample of groups ( students – doctors – employee).
Area sample:
Used when for samples that represents different geographical area and the geographical areas are chosen in a randomly or non-random way.