187 Views

SAMPLING AND EXPERIMENTATION

Sampling is examining by taking a sample -a part representing the whole (population).

Types of Sampling

1. Random Sampling

– Selection of members of a group haphazardly where every item has an equal chance of being selected e.g. to select 5 students to go for a tour from a class:

• Class members write their names on pieces of paper
• They are folded and put in a basket
• The basket is shaken and fives papers are taken out
1. Systematic Sampling

-Selection of members of a sample from an evenly distributed phenomena at regular intervals e.g. after every 10 items/members.

1. Stratified sampling

-Selection of members of a sample by breaking the population into homogenous groups e.g. to select 6 students to go for a tour:

• Break the class into boys and girls
• Select 3 student from each group by random or systematic sampling
• Combine units from each group to form the required sample.
1. Cluster Sampling

-Selection of sample by dividing the sample into clusters with similar characteristics then a sample is taken from each cluster and representative choices from each cluster are combined to form a sample e.g. to sample the housing cost an estate is chosen to represent each group and representative choices are chosen from each estate and combined to form a sample.

1. a) It’s less expensive
2. b) It saves time
3. c) It avoids bias

2. b) Systematic sampling to an evenly distributed population

Experimentation

Experimentation – Conducting a test or investigation to provide evidence for or against a theory e.g. to determine the chemical composition of rocks and soils.