DAR Quantitative Data Assignment 2022-23

Small-scale excavations at the (fictitious) Iron Age site of Hollerton have yielded an assemblage of 180 pottery sherds from three horizons:

Horizon 1 Upper     0–25 cm;

Horizon 2 Middle   26–52 cm;

Horizon 3 Lower     53–65 cm.  

Each sherd has been recorded as coming from the rim, side or base of a vessel, and the depth from which it was excavated is also recorded. Where possible, the rim diameter of the original pots has been estimated from the rim sherds. For the 61 rim diameter estimates, Table 1 gives the depths in centimetres from the surface of the excavation at which the sherd was found and the diameter in centimetres of the rim of the vessel. Table 2 summarises the distribution of sherd types across the three horizons.

Analysis 1. Rim diameters

The excavator wishes to know whether there is any noticeable change in size of vessels through time. Obviously, the more deeply buried each sherd was, the older it is likely to be.

Using the data in Table 1, please carry out the following tasks, using Excel:

1. Calculate the mean rim diameter for the whole dataset.

2. Group the diameter estimates by horizon. Calculate the mean size in each horizon and the increase in mean size between consecutive horizons.

3. Plot all the data from Table 1 on an appropriate Excel chart. Choose what you think is the most appropriate format and type of chart to explore and to understand any possible trend.

4. Make sure that the chart is well-presented with labels for all key parts and a title – it should of a finished standard ready for presentation in a publication or a poster.

5. Explain briefly (200 words max) why you have chosen the chart type that you have.

6. Explain briefly (200 words max) what trends you think can be seen in this data, how reliable any such trends are likely to be and what you think they might tell us about pottery from this site, and its uses.

Analysis 2. Fragment distribution

In addition, the excavator would like to know if the different types of sherds are associated with particular horizons, or randomly distributed. Using the data in Table 2, Please carry out the following tasks, using Excel:

7. Use a chi squared test, as shown in the practical session, to investigate the hypothesis that there is no difference in the prevalence of each type of fragment across the horizons in this trench. Your answer should include, as a minimum, the null hypothesis that you are testing, the chi-squared statistic, the value of alpha you are testing against, the calculated p value and the number of degrees of freedom for the test you perform.

8. Comment briefly on your findings and what they might imply about the use of pottery at Hollerton (max 100 words).

Carry out the tasks using Excel. Copy-and-paste appropriate parts of your calculations and charts into a Word document for submission.