An Investigation Into An Aspect Of Human Variation.

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An Investigation Into An Aspect Of Human Variation

Aim

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

Hypothesis

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.

Variables

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.

iii) Sampling - In order to decide upon the individuals that will be sampled in the investigation, a random sampling technique was applied. In this way individual bias was prevented, creating a fairer experiment. By incorporating a random sampling technique, variables such as race, socio economic groupings and underlying medical conditions, that may have some effect on an individuals foot length or hand span, could be taken into account.

In the design of this investigation, I stated that eighty people would be sampled. However, I decided to sample one hundred people (fifty males and fifty females), as results collected from fewer individuals would give rise to greater anomalies. By taking a larger sample, readings can be taken from a broader cross section of the population so that a more accurate view of the correlation between foot length and hand span could be gained.

iv) Environment - Each human being has a slightly different environment that will affect the way in which they grow and develop. However, differences in environment should not affect the feet and hands separately and therefore individuals with varying environments, home life or backgrounds could still be compared without excessive anomalies.

v) Measurements - In this investigation the right foot length and right hand span of individuals was measured and compared. By measuring the right hand and foot only, differences between the right and left hand and the right and left foot could be taken into account. To do this effectively, the foot length and hand span was clearly defined so that measurements were taken consistently and compared accurately. All measurements were taken using a standard metre long tape measure. Each measurement was recorded to the greatest degree of accuracy possible (nearest millimetre).

Hand span: The hand span was measured from the tip of the thumb to the tip of the little finger when the hand and fingers are stretched out flat on a surface. This measurement excluded any length of fingernails extending past the ends of the fingers. By defining the hand span to be measured, discrepancies between measurements should have been reduced giving rise to more accurate and reliable results.

Foot length: The foot length was measured from the back of the heel to the end of the big toe when placed on a flat surface. This measurement excluded any nail extending over the end of the toe. By defining the foot length to be measured, discrepancies between measurements should have been minimised giving rise to more accurate and reliable results.

Apparatus

The apparatus required for this investigation were a standard metre long tape measure, a clipboard and writing implements.

Procedures

One hundred people (fifty male and fifty female) were sampled in this investigation considering and controlling the variables as listed under 'Variables'. I have increased the number of people sampled from eighty, as stated in the design, to one hundred; a larger sample will give a better representation of the population and reduce the extent of any anomalies when averages are taken. Each individual was selected by random sampling. This involved numbering people and using a random number generator to select the people to be measured. A random sampling technique was used to increase the accuracy of the investigation by removing individual bias. By incorporating a random sampling technique, variables such as race, socio-economic groupings and underlying medical conditions, that may have some effect on an individuals foot length or hand span, were taken into account. Each person had their right foot length and right hand span measured (using a tape measure according to the defined lengths) and recorded in a table. Each measurement was carried out in a consistent and methodical manner so that accurate readings could be obtained.

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Results

By measuring the length of the foot and the hand span, quantitative rather than qualitative data has been obtained and recorded in tables, charts and graphs. This way the results have been displayed in forms in which any correlation is clearly visible. To determine whether there is correlation between hand span and foot length in humans, several statistical techniques have been applied. For example, Spearman's Rank Correlation Coefficient has been used to determine whether correlation is present, positive or negative and its associated strength. Scatter graphs have also been used to illustrate any correlation graphically so that any relationship ...

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