1. Sampling and
Experimentation:
Planning and Conducting a Study
Data must be collected according to a welldeveloped plan if valid information on a
conjecture is to be obtained. This plan includes
clarifying the question and deciding upon a
method of data collection and analysis.

2. Methods of Data Collection
• Census: a study that obtains data from every
member of a population.
• Sample Survey: a study that obtains data from a
subset of a population.
• Experiment: a controlled study in which the
researcher attempts to understand cause and
effect relationships.
• Observational Study: researcher attempts to
understand cause and effect relationships in an
uncontrolled environment.

3. Factors to consider before selecting a
data collection method
There are multiple methods and tools that can be
used to collect data, but you must decide which
method will best answer your research
questions. Before you select an appropriate data
collection method, there are three main factors that
should be carefully considered:
• Consider the purpose for conducting the evaluation.
• Consider the evaluation design.
• Carefully consider the availability of resources for the
project.