STRATIFIED SAMPLING
In a stratified sample, the population is first divided into categories and the number of members in each category is determined. The sample is then made up of these categories in the same proportions as they are in the population. Random sampling chooses the required numbers in each category. In a random sample, every member of the population has an equal chance of being chosen.
To obtain a sample of 60 students stratified according to Year 10 and Year 7; I will have to calculate the number of boys from Year 10 and Year 7, which must be represented in the sample.
Altogether there are 1013 (one thousand and thirteen) students in our school. To work out the proportion of boys in Year 10 and Year 7, First of all I found out how boys were in Year 10 and Year 7. I added these together to get 199(one hundred and ninety-nine). Then I got the number of boys in each year and divided it by the total (199) and then multiplied it by 60(sixty). I rounded this answer to a whole number. This is because it would be an easier number to work with and you cannot round people to decimal places or significant figures.
In my survey, I went to the school office and I got all of the boy’s names in Year 10 and Year 7 on two separate pieces of paper. By each name was a number. To find out which boys from Year 10, I had to ask to estimate the length of the straight line, I put all the boys names in Year 10 in a hat and picked the amount of boys needed to estimate the length. I did the same with the Year 7 boys. I already knew how many boys I needed to ask from each year because I had already done a stratified sample and worked out the numbers needed.
Example 1: In Year 10 there are 110 boys.
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Example 2: In Year 7 there are 89 boys
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Now I have collected all the information, it is time to do my Survey. I will draw an accurately measured line and ask the proportion of boys in Year 10 and Year 7 to estimate the length of the line. I found out the proportion of the boys in Year 10 and Year 7 by doing a stratified sample.
My next step is to do a pilot study. I will ask about five boys in Year 7 and Year 10 to ensure my coursework is done to a high-quality standard and my question does not seem to force an answer out of them. From the pilot study I will also be able to tell if my survey is grammatically correct. When I say this, I mean if the spelling, punctuation, and grammar are all correct.
SPECIFICATIONS FOR MY SURVEY
Paper with survey must be held approximately the same distance from each participant so that everyone sees the survey as well as each other. If the survey is held closer, it may give the student a better idea of the line’s length.
Weather conditions must be similar – if it is cloudy, there is less light for the contestant to see the paper with and they are not given as good a view as if it were a sunny day.
Survey must be done during school hours so that most of the subjects are in a similar frame of mind.
No items of measurement should be nearby, so that the subject has nothing to compare the line/angle to.
60 people must take part in the survey
All participants must be asked whether they are able to see the diagrams clearly.
Exactly the same words must be used when explaining about the survey
The participant must spend no more than two minutes (after pilot study –
The student may not communicate with anyone else who is able to view the paper or who has done the survey.
PILOT STUDY
I performed my pilot study and I found out that my survey was done to a good standard was understandable and got to the point. The boys I tested it on commented that it was set out well and did not need altering. One thing they all asked me was, “Did I get it Right” or “How much was I off by”. This made me think for a while and in the end I concluded that I should a ‘Deviation’ and a ‘Percentage Error’ column in my results table.
