Table 1.

Summary of statistical test results (Minitab), using both 1- and 2-tailed t-tests (assuming normal distribution) and Mann–Whitney tests (assuming non-normal distribution)

	Is Trafalgar Square younger than Aveley/Lion Pit?		Is Aveley/Lion Pit younger than Purfleet?		Is Purfleet younger than Swanscombe?
	Yes	No	Yes	No	Yes	No
Valvata (1-tailed t-test)	8	0	6	2	7	1
Valvata (2-tailed t-test)	8	0	5	3	6	2
Valvata (1-tailed MW-test)	8	0	5	2	7	1
Valvata (2-tailed MW-test)	8	0	4	4	7	1

The results of each duplicate analysis are included in order to provide a statistically significant sample size.

Number in “Yes” column represents the number of amino acid (AA) fractions that enable discrimination between the two Thames sites in question, and also supports their stratigraphical position at a 95% confidence level.

Number in “No” column represents the number of AA fractions that do not enable discrimination between the two sites.

For example: In the 2-tailed t-tests, analysis of Valvata shell results in eight out of eight AA fractions supporting the hypothesis that Trafalgar Square is distinguishable and younger than Aveley/Lion Pit; only six out of eight support the hypothesis that Swanscombe is older than Purfleet.

Full details of the statistical tests are given in the Online Supplement Worksheet 3.