Statistics in Biology

• Standard deviation


  A measure of variability that describes an average distance of every score from the mean-if standard deviation of two varibales do not overlap, there is a statistically significant difference
• Why would you chose standard deviation over the range?

  -shows spread of data rather than just highest or lowest-reduces effect of anomalies
• What is better than standard deviation?

  Students T test-judges the significance in the difference between two sample means
• T values and P values

  -if the T value is higher than the critical value then there is a statistically significant difference between the two variables. Reject the null hypothesis.-the P value should be less than 0.05 (as biology needs a 95% confidence level)
• Null and alternative hypotheses


  NullThere is not a statistically significant difference between variables x and y. Any difference is due to chance.AlternativeThere is a statistically significant difference between variables x and y. The difference is not due to chance.