A-Level Edexcel Biology Dispersion and Range

Review A-Level Edexcel Biology dispersion, standard deviation and range through the available evidence on mean-and-range calculations in inhibition-zone data.

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Soil contains many types of organisms such as earthworms.

(a)

A scientist investigated the mass of earthworms present in the soil of a 5-year-old plantation and a 15-year-old plantation. The method used in each plantation was: - five sample sites were selected at random - a block of soil with an area of $25 \mathrm{~cm} \times 25 \mathrm{~cm}$ and to a depth of 10 cm was removed at each site - the total mass of earthworms present in each block of soil was recorded.

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(i)

The tables show the results of this investigation.

Table for Question (i) — Edexcel A-Level Biology A2

Calculate the standard deviation for the mass of earthworms present in the soil of the 15-year-old plantation. Use the formula:

s=\sqrt{\frac{\sum(X-\bar{X})^{2}}{n-1}}

Where: n is the number of sample sites X is the mass of earthworms from one sample site $\bar{X}$ is the mean mass of earthworms

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(ii)

Describe how the means and standard deviations could be used to compare the results from these two plantations.

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A.1.10—Dispersion, standard deviation and range question 1

Question (a)

Question (i)

Question (ii)