Statistical Analysis Graphing

Understanding Statistical Analysis in Biology

📊 Standard Error of the Mean (SEM)

SEM measures how precisely we know the true population mean from our sample.

• Smaller SEM = more precise estimate
• Larger sample size = smaller SEM
• Used to create error bars on graphs

📈 Error Bars (±2×SEM)

Error bars show the uncertainty in our measurements.

• Represent ~95% confidence interval
• Show precision of the mean
• Help visualize data variability

🎯 Statistical Significance

When error bars don't overlap, the difference is likely real, not due to chance.

Control

Experimental

✓ Significant Difference

🤝 No Significant Difference

When error bars overlap, we cannot conclude the groups are different.

Control

Experimental

✗ No Significant Difference

Protein Expression: Gene X Wildtype vs Mutant

Protein expression levels are measured in cultured HeLa cells using Western blot analysis with fluorescent antibodies. Cells are grown under identical conditions (37°C, 5% CO₂) in complete media for 48 hours before protein extraction. Expression is normalized to GAPDH housekeeping protein to ensure accurate comparison. The control group has wildtype Gene X (normal gene variant found in healthy populations), while the experimental group has a specific point mutation in Gene X (A234V substitution). This mutation was identified in a genome-wide association study but its functional significance is unknown. The experiment tests whether this genetic variant affects protein production levels.

Step 1: Calculate Statistics

Control Group Data

Trial	Value (relative units)
1	42.0
2	45.0
3	43.0
4	44.0
5	41.0

Experimental Group Data

Trial	Value (relative units)
1	41.0
2	44.0
3	42.0
4	43.0
5	40.0

Control Group Calculations

Mean:

Experimental Group Calculations

Mean:

Statistical Analysis Graphing

Protein Expression: Gene X Wildtype vs Mutant

Step 1: Calculate Statistics

Control Group Data

Experimental Group Data

Control Group Calculations

Experimental Group Calculations

Step 3: Interpret Statistical Significance

Step 2: Create Your Graph

Understanding Statistical Analysis in Biology

📊 Standard Error of the Mean (SEM)

📈 Error Bars (±2×SEM)

🎯 Statistical Significance

🤝 No Significant Difference

How to work through this activity

Formulas

Protein Expression: Gene X Wildtype vs Mutant

Step 1: Calculate Statistics

Control Group Data

Experimental Group Data

Control Group Calculations

Experimental Group Calculations

Step 3: Interpret Statistical Significance

Step 2: Create Your Graph