Section 1 Application Flashcards
(50 cards)
Why is power analysis important before starting an experiment?
To ensure enough participants are included to detect a real effect while avoiding ethical issues from oversampling.
How does increasing variance affect statistical power?
Higher variance reduces power — more variability makes it harder to detect true differences.
In clinical research, why is a sample too small unethical?
Because it exposes patients to risk without sufficient statistical chance of detecting an effect.
What would you change if your study is underpowered?
Increase sample size or seek larger effect sizes.
Why is post-hoc power analysis discouraged?
It assumes an effect exists despite non-significant results, introducing circular reasoning.
Why is effect size independent of sample size?
Effect size reflects the magnitude of difference; it doesn’t change with more participants, only statistical power does.
Why is α usually set at 0.05?
Balances risk of false positives while maintaining sensitivity; standard convention in biomedical research.
Why might a smaller α increase β?
Lowering α makes it harder to reject the null, thus increasing risk of Type II error.
What role does variance reduction play in study design?
Controlling variance (e.g. through better measurement) boosts power without needing huge sample sizes.
Why include pilot studies before large trials?
Estimate variance and effect size to inform appropriate sample size calculations.
Why is hydrodynamic focusing critical in flow cytometry?
Ensures single-cell alignment for precise laser interrogation and measurement.
Why are multiple fluorochromes used?
To detect multiple markers simultaneously (multiplexing) using different emission wavelengths.
Why do you need compensation in multi-color flow cytometry?
Corrects for spectral overlap between fluorochrome emission spectra.
When would you use FSC vs SSC?
FSC = cell size
SSC = granularity/internal complexity
Why is gating essential?
Isolates specific cell populations for focused analysis.
Why is single-cell suspension critical before analysis?
Prevents clumps that would give inaccurate scatter/fluorescence signals.
Why do you include viability dyes?
Excludes dead cells that may non-specifically bind fluorochromes.
Why are PMTs often preferred over photodiodes?
Higher sensitivity allows detection of low-intensity fluorescence.
Why can high event rates cause doublet discrimination issues?
Multiple cells may pass through the laser together, falsely interpreted as one event.
How does increasing laser power affect sensitivity?
Improves fluorochrome excitation but risks increasing background noise and photobleaching.
Why are indirect enzyme assays often better for high-throughput?
They allow fast, parallel detection using fluorescence, reducing manual handling.
Why is fluorescence preferred over chromatography in high-throughput?
Faster, parallel, requires less separation, suitable for automation.
Why might optical assays be limited in field testing?
Require specific equipment and controlled conditions, while simple pH indicators can give visible readouts.
What makes continuous assays more suitable for automation?
They allow real-time signal monitoring without stopping reactions.
