Sample Size Power Analysis Flashcards
A too small sample size can lead to what?
UNDERPOWER, leading to findings that may be invalid or never disseminated
Why is sample size calculation a necessary first step?
To balance statistical needs with issues of feasibility
Type 1 Error
False Positive
Type 2 Error
False Negative
Power = 1-B
The probability of correctly rejecting the null hypothesis when it is false
Power Analysis
Sample size calculation for hypothesis-testing studies where a researcher uses a predetermined a and attempts to achieve a desired level of B
What information is NECESSARY to compute sample size using power analysis?
- Knowledge how the primary endpoint is measured
- Type of hypothesis test proposed
- Measure of variance or precision
- Specification of the magnitude of effect one wishes to detect
- Specified significance level (a)
- Target level of power (1-B)
Required Sample Size for a study increases with what?
- Increasing Variance
- Decreasing Probability of Type 1 Error
- Increasing Desired target level of Power
- Decreasing size of the effect of interest
The purpose of the study could be either what?
Descriptive or Analytical
Descriptive Studies
An investigation of a disease or event
Analytical Studies
Understanding the relationship and/or causal mechanism that may exist between two or more variables
The time orientation could be classified as what?
Prospective or Retrospective
Prospective Studies
Researcher collects the data after the study onset by following individuals over a period of time
Retrospective Studies
Evaluation of data of past events or existing data such as medical records to achieve the research objective
Types of Experimental Designs
- RCT
- Quasi
