Statistics Coursework
When standing at the station waiting for my bus home, I noticed some year seven boys from St Olaves introducing themselves to one and other. They were talking to each other about their experiences of their first week at a new school when I noticed that they were a lot smaller than I remember myself and my friends being in year seven. I then began to think about general heights of boys and girls, wondered if girls were always taller than boys. I decided to investigate this.
I predict that girls in year seven will be taller than boys in year seven.
I will attempt to either disprove or prove my hypothesis by taking the averages of heights of a sample of year seven boys and a sample of the year seven boys.
The Data I am using is Secondary, as somebody else collected it, for me. The fact that this data is Secondary can leave me with some problems. When collected the data, people may have forgotten to take their shoes off. They may have also measured in feet and inches and translated it roughly by the means of stating the one inch equals two point five centimetres. Though this is correct, the conversion from one type of measurement to another could have resulted in a loss of accuracy. People may also have added their hair into their height. If I were collecting the data myself, I would have been able to ensure that the data was all collected absolutely accurately.
Other things that could have biased my results are the fact that the data
So I can begin to find averages and draw conclusions from my data, I need to take a sample of the records. There are three types of sample I could take to find the data records I want to use in my coursework; a Simple Random Sample, a Systematic Sample and a Stratified Sample.
Simple Random Sampling:
A Simple Random sample is one in which everyone has an equal chance of being chosen. To take a Simple Random Sample, I would use a random number generator on my calculator and selecting the students data by corresponding the number that appears on my calculator with the number I have given each student.
Systematic Sampling:
Systematic sampling is when every nth member of the population is chosen. To find what n is I would have to divide the population by the sample size. Although not everyone has an equal chance of being chosen, and the sample is not entirely random, it is still representative.
Stratified Sample:
I would split the population into groups and use the formula:
Number in the group ¸ population x sample size.
This would give me a sample that is representative of each group. This is a good method, because I will get a fair representation of all my data, but there are no groups that I could split my sample into.
