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An Investigation Into An Aspect Of Human Variation.

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An Investigation Into An Aspect Of Human Variation


The aim of this investigation was to explore and analyse an aspect of human variation.


There will be a positive correlation between an individual's foot length and their hand span. This may be due to linkage; the genes that create these characteristics may be positioned on the same chromosome so that they become linked, and are inherited together. This linkage causes the two characteristics to become associated so that a person with large feet will also have large hands.


In order to create a fair investigation, it was necessary to consider the variables that affect an individual's foot length or hand span. Any variables that were likely to disrupt the results were controlled and those measured were recorded accurately so that any correlation could be observed and evaluated successfully.

i) Age - The majority of individuals stop growing by the age of eighteen. Below this age, people grow at different rates and for this reason, cannot be compared accurately. In this investigation, the sample included only, people above the age of seventeen. Above this age, most people will have attained their maximum growth and therefore their maximum foot length and hand span.

ii) Gender - The average male is ten centimetres taller than the average female. It follows that this difference will also be translated in an overall trend that males will have greater foot lengths and hand spans. In order to take into account of this variable, equal numbers of males and females were sampled. The results of this investigation have been analysed with males and females together and each gender independently so that any differences across the sexes can be examined and their strength determined.


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Standard Deviation







Range of data







The 'Range of data' gives the highest and lowest values of the data recorded in the investigation.

Appendix 2-Graph 1 - 'A scatter graph to show the correlation between hand span and foot length', contains the results of the measurements of both the males and females of the one hundred individuals sampled. A trend line has been plotted to gain a clearer indication of the correlation between hand span and foot length. The trend line shows very clearly that there is strong correlation between hand span and foot length with the larger hand spans occurring with the larger foot lengths. Although there is a wide variation, the points are clustered closely around the trend line indicating strong correlation. The points on the graph appear to be clustered in two groups one around a hand span of 16-20cm and the other from 20-24cm. This has been highlighted on a copy of the graph below:

This may indicate a divide between the foot length and hand span of males and females.

Appendix 3-Graph 2 is a scatter graph plotted with the data gained from female individuals. The trend line shows clearly a strong correlation between their hand span and foot length. Although some anomalies are present e.g. a hand span of 21cm and foot length 23.5cm, the majority of points are clustered closely around the trend line increasing the significance of the correlation.

Appendix 4-Graph 3 is a scatter graph plotted with the data gained from male individuals. The trend line plotted from the data demonstrates a clear positive correlation between their hand span and foot length. Although there are anomalies present similar to the data in Appendix 3 Graph 2, such as the measurement of hand span 21.4cm and foot length 25.

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Mutation - The organism is dependent on the environment for the raw materials for growth, but growth is also regulated internally. Because the size and form of an individual is under genetic control, events such as the rate and site of cell division and the extent of cell enlargement can be affected by mutations. A mutation caused by a random change in the DNA base sequence and therefore an alteration in a polypeptide coded for may result in unusually large or small hands or feet. This random occurrence may have caused anomalous results in the investigation.

Experimental error - Inaccuracies in measuring the hand spans and foot lengths of individuals may have caused anomalous results. For example the majority of people sampled wore socks that may have differed in thickness, causing the foot length measurement to be inconsistent. In a future experiment this flaw could be corrected by ensuring that all individuals were sampled bare foot.

In this investigation, measurements were recorded to the nearest millimetre. The mean value for hand span was 20.3cm and the mean value for foot length was 25.9cm. Each of these values were measured to the nearest millimetre creating a probable error of 20.3cm ± 0.5mm and 25.9cm ± 0.5mm. This leads to a percentage error in this investigation of around2% in every measurement. This consistent level of inaccuracy should not have had a significant effect on the results of this investigation which were needed for comparative purposes on the scatter graphs. The accuracy of this investigation is sufficient to provide strong evidence to support the hypothesis 'there will be a positive correlation between an individuals foot length and hand span'. The anomalies in this investigation, although present, are not adequate to question the results and conclusions. However, in a future investigation an improvement on this accuracy through more precise measuring equipment and other improvements outlined above, might create even stronger correlation and greater evidence to support the hypothesis.

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