1. Using Statistics in Biology

2. Histogram

3. Mean (x̄) is a measure of the central tendency of a set of data.
Ex. Calculate the mean.
Answer = 11.6

4. Graphing the Mean  Bar Graph

5. Error bars are a graphical representation of the variability of data.

6. Measures of Variability
Range: difference between largest/smallest values in data set
Standard deviation (s) is a measure of the spread of most of the data

7. 68% of all data fall within ± 1 standard deviation of the mean

9. Measurements of Confidence
Uncertainty: the margin of error in a measurement
Eg. digital scale: 126.4g (±0.1g)

10. Standard Error of the Mean (SE or SEM): measures how close the sample mean is to the population mean
The greater the sample size, the less the uncertainty in the calculations

11. 95% confidence interval (95% CI):
95% confident that the true means falls between 2 SE above/below calculated mean
Graph with error bars representing SE of the mean
Graph with error bars representing 95% confidence interval

12. Significance of Data
Which graph shows two means that are significantly different? Hint: Look for the non-overlapping error bars.
Answer: The means in (c) are statistically different.