Analyzing biological data: mean, standard error and the chi-square test

Learning objectives

Calculate the mean, median, range and standard deviation of a data set, and explain what each measure tells you about the sample

Calculate the standard error of the mean, add error bars of ±2 standard errors to a graph, and explain that a larger sample size reduces standard error

Justify a claim about whether two treatment means differ meaningfully by deciding whether their error bars overlap, and explain the limits of that conclusion

State an appropriate null hypothesis, calculate the chi-square statistic from observed and expected counts, and determine the degrees of freedom for the test

Compare the calculated chi-square value with the critical value at p = 0.05 to reject or fail to reject the null hypothesis, and state the conclusion in terms of the biological question

Select the correct graph type for a data set, label both axes with units, and describe a trend using specific values read from the graph