Studies design (Statistics)

Refer to Khan academy course.

Types of studies:

• Sample study: To estimate ONE certain parameter of a population.
• Observational studies: To compare TWO parameters of a population WITHOUT affecting them.
• Experiments: To compare TWO parameters of a population and DOES affecting one and does not affecting the other one.

Samples or surveys

• Problem 1: Qualitative and quantitative data
• Problem 2: Representative samples
• Problem 3: Biased wording in survey questions
• Problem 4: Sampling methods
• Systematic sampling: 100% members of ALL groups chosen.
• Stratified sampling: Some members from ALL groups chosen.
• Random sampling: An adequate number of members chosen, each an equal chance of being in the sample.
• Cluster sampling: 100% members from SOME groups are chosen.

Observational studies & experiments

• Observational study: Measure or survey members of a sample WITHOUTtrying to affect them.
• Controlled experiment: Apply some treatment to one of the groups, while the other group does not receive the treatment.

Notes

• Randomized experiments are designed to suggest causation
• Correlation is WEAKER than causation
• To answer a question about a causal relationship, we need to perform an experiment with a treatment group and a control group.
• While sample study need a part of relative members, Observational studyneed ALL members.