Where do I find mark scheme for this past paper question?

I am not sure what year this question was from but it is a old paper

The earthworm, (Lumbricus terrestris), feeds on dead organic matter found in soil. Soil pH is one of the abiotic factors that affects the population size of earthworms. The populations of earthworms in fields with either acidic soil or alkaline soil have been investigated. The results of this investigation are summarised in the table.

- Describe a sampling method that could be used to collect the data in this table

- Explain how differences between the mass of earthworms in these two soild could be shown to be statistically significant