AP Biology Statistical Analysis Graphing App

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

Step 1: Calculate Statistics

Instructions: Calculate the mean, standard deviation, and standard error for each group. Enter your answers to 2 decimal places. Tolerance: ±5% of correct answer.

Control Group Data

Trial	Value

Experimental Group Data

Trial	Value

Formulas:
Mean = Σx / n
SD = √(Σ(x - mean)² / (n-1))
SEM = SD / √n
Error bars = Mean ± 2×SEM

Statistical Significance:
If ±2×SEM error bars don't overlap → ~95% confidence of significant difference

Control Group Calculations

Mean:

Experimental Group Calculations

Mean:

Step 2: Create Your Graph

Complete all calculations to begin graphing