Hypothesis Formulation and Sampling
Null vs Alternative & Directional vs Non-Directional
Null Hypothesis (H₀)
States there is no significant difference or relationship between variables. It is the hypothesis that the researcher tries to disprove or reject.
Alternative Hypothesis (H₁ or Hₐ)
States there is a significant difference or relationship. It represents what the researcher actually expects to find.
Directional Hypothesis
Predicts the specific nature (direction) of the relationship (e.g., "Group A will score higher than Group B").
Non-Directional Hypothesis
Predicts a relationship or difference exists, but does not specify the direction (e.g., "There will be a difference between Group A and B").
Probability Sampling Methods
Every element in the population has a known, non-zero chance of being selected.
Non-Probability Sampling Methods
Selection is based on non-random criteria; not every element has a chance of being included.
Sampling Bias & Determining Sample Size
Sampling Bias
Occurs when some members of the intended population have a lower or higher probability of selection than others. Threatens the external validity (generalizability) of findings.
Mitigation: Use random sampling where possible, define the target population clearly, and monitor response rates.
Determining Sample Size
- Statistical Power: Larger samples generally yield higher power to detect true effects.
- Margin of Error / Confidence Interval: Determines precision of estimates.
- Population Heterogeneity: More diverse populations require larger samples.
- Practical Constraints: Time, cost, and access to participants.
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