- the variations in Hair Colour
- the variations in Eye Colour
- the relationship between the above two colours
- the distances travelled to school
- the relationship between height and weight
- the relationship between two sets of Key Stage 2 results
- the relationship between IQ and Key Stage 2 results
- the height to weight ratio in terms of the body mass index.
I have decided to choose, option 5: The relationship between height and weight.
Hypothesis
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I think that the taller one person is the more weight the person will have.
- The higher the year of the student, the higher the height and weight values will be.
- Boys will be taller and heavier than girls in general.
To find out if my Hypotheses are correct I will need to use the information of a sample of the 1183 students available.
I will use a sample of 120 students, with equal amounts of male and female participants. (60 males and 60 females APPOX)
To make it a fair sample, i.e. unbiased, I will need to use a method called stratified sampling. This helps to eradicate any allegations of being biased by looking fairly at ratio students in each group.
Sampling Methods
Random sampling is the purest form of probability sampling. Each member of the population has an equal and known chance of being selected. When there are very large populations, it is often difficult or impossible to identify every member of the population, so the pool of available subjects becomes biased.
Systematic sampling is often used instead of random sampling. It is also called an Nth name selection technique. After the required sample size has been calculated, every Nth record is selected from a list of population members. As long as the list does not contain any hidden order, this sampling method is as good as the random sampling method. Its only advantage over the random sampling technique is simplicity. Systematic sampling is frequently used to select a specified number of records from a computer file
Stratified sampling is commonly used probability method that is superior to random sampling because it reduces sampling error. A stratum is a subset of the population that shares at least one common characteristic. The researcher first identifies the relevant stratums and their actual representation in the population. Random sampling is then used to select subjects from each stratum until the number of subjects in that stratum is proportional to its frequency in the population. Stratified sampling is often used when one or more of the stratums in the population have a low incidence relative to the other stratums.
I used stratified sample using this formula:
Amount of people of the same sex in the year
Amount of people in school X120
This is what I achieved from that:
I then was able to use random numbers to find my sample. E.g. 13 random numbers for year 7 females.
These are the randomly generated numbers
Formulae used for each stratified sample
This is the original amount of students (1183)
