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Stratified Random Sampling. After producing a questionnaire for your survey (see Questionnaires and Surveys) you will need to organise a sample. Pilot survey:. Test the questionnaire on a few people first to see if it works OK or needs amending. Sample Size and Type:.

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## Test the questionnaire on a few people first to see if it works OK or needs amending.

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**Stratified Random Sampling**After producing a questionnaire for your survey (see Questionnaires and Surveys) you will need to organise a sample. Pilot survey: • Test the questionnaire on a few people first to see if it works OK or needs amending. Sample Size and Type: • Decide on the size and type of the sample that you intend to use. Will it be a simple randomsample or a stratified random sample?**Bilton High School**Year 7 Year 8 Year 9 Year 10 Year 11 Stratified Random Sampling Stratified Random Sampling can be used where the population under consideration separates naturally into sub-groups or strata. Once each of the subgroups/strata have been identified we then take a simplerandom sample from each one.**Bilton High School**Stratified Random Sampling Stratified Random Sampling can be used where the population under consideration separates naturally into sub-groups or strata. Year 7 156 students 180 students Year 8 The numbers taken in each of these samples is proportional to the size of the group. 224 students Year 9 196 students Year 10 Year 11 210 students**Bilton High School**Stratified Random Sampling Example Question 1: As part of a survey on attitudes to homework a stratified random sample of size 60 is to be taken from students at Bilton High School. Find the sample size for each year group. The total number of students = 966 Year 7 sample size = 156/966 x 60 = 10 students Year 8 sample size = 180/966 x 60 = 11 students Year 9 sample size = 224/966 x 60 = 14 students Year 10 sample size = 196/966 x 60 = 12 students Year 11 sample size = 210/966 x 60 = 13 students**Bilton High School**Stratified Random Sampling Question 1: As part of a different survey on attitudes to school meals in Lower-School a stratified random sample of size 40 is to be taken. Find the sample size for each year group. The total number of Lower-School students = 560 Year 7 sample size = 156/560 x 40 = 11 students Year 8 sample size = 180/560 x 40 = 13 students Year 9 sample size = 224/560 x 40 = 16 students**Bilton High School**Stratified Random Sampling Example Question 2: A survey is to be conducted on whether more after-school clubs are needed in Lower school. A stratified random sample of size 50 is to be used. How many girls from year 8 should be in the sample? The total number of Lower School students = 560 Year 8 girls sample size = 96/560 x 50 = 9**Bilton High School**Stratified Random Sampling Question 2: A survey is to be conducted on whether more after-school clubs are needed in Lower school. A stratified random sample of size 50 is to be used. How many boys from year 7 should be in the sample? The total number of Lower School students = 560 Year 7 boys sample size = 70/560 x 50 = 6**Bilton High School**Stratified Random Sampling Question 3: A survey is to be conducted on whether more after-school clubs are needed in Lower school. A stratified random sample of size 50 is to be used. How many boys from year 9 should be in the sample? The total number of Lower School students = 560 Year 9 boys sample size = 100/560 x 50 = 9**Stratified Random Sampling**Example Question 3: There are 37,600 people in a town who can vote in a local election. They are categorised by age and gender as shown in the table below. A market research company intends to take a survey of the voting intentions of 1800 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Female aged under 40 (b) Male (c) Aged 40 or over (a) 7600/37600 x 1800 = 364 (b) 17900/37600 x 1800 = 857**Stratified Random Sampling**Example Question 3: There are 37,600 people in a town who can vote in a local election. They are categorised by age and gender as shown in the table below. A market research company intends to take a survey of the voting intentions of 1800 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Female aged under 40 (b) Male (c) Aged 40 or over (a) 7600/37600 x 1800 = 364 (b) 17900/37600 x 1800 = 857 (c) 23600/37600 x 1800 = 1130**Stratified Random Sampling**Question 4: A town in a different part of the country has 33 800 people who are eligible to vote . They are categorised by age and gender as shown below. A different market research company intends to take a survey of the voting intentions of 2500 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Male aged under 30 (b) Female (c) Aged under 30 (a) 5400/33800 x 2500 = 399 (b) 15900/33800 x 2500 = 1176**Stratified Random Sampling**Question 4: A town in a different part of the country has 33 800 people who are eligible to vote . They are categorised by age and gender as shown below. A different market research company intends to take a survey of the voting intentions of 2500 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Male aged under 30 (b) Female (c) Aged under 30 (a) 5400/33800 x 2500 = 399 (b) 15900/33800 x 2500 = 1176 (c) 10200/33800 x 2500 = 754**Stratified Random Sampling**Question 5: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Males on part-time courses (b) Female (c) Full-time students (a) 2300/9000 x 400 = 102 (b) 4800/9000 x 400 = 213**Stratified Random Sampling**Question 5: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Males on part-time courses (b) Female (c) Full-time students (a) 2300/9000 x 400 = 102 (b) 4800/9000 x 400 = 213 (c) 4000/9000 x 400 = 178**Stratified Random Sampling**Question 6: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Females on full-time courses (b) Male (c) Part-time students (a) 2100/9000 x 400 = 93 (b) 4200/9000 x 400 = 187**Stratified Random Sampling**Question 6: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Females on full-time courses (b) Male (c) Part-time students (a) 2100/9000 x 400 = 93 (b) 4200/9000 x 400 = 187 (c) 5000/9000 x 400 = 222**Worksheets**Y 7 Y 8 Y 9 156 180 224 Example Question 1: As part of a survey on attitudes to homework a stratified random sample of size 60 is to be taken from students at Bilton High School. Find the sample size for each year group. Question 1: As part of a different survey on attitudes to school meals in Lower-School a stratified random sample of size 40 is to be taken. Find the sample size for each year group.**Y 7**Y 8 Y 9 Boys 70 84 100 Y 7 Y 8 Y 9 Girls 86 96 124 Boys 70 84 100 Girls 86 96 124 Example Question 2: A survey is to be conducted on whether more after-school clubs are needed in Lower school. A stratified random sample of size 50 is to be used. How many girls from year 8 should be in the sample? Question 2: A survey is to be conducted on whether more after-school clubs are needed in Lower school. A stratified random sample of size 50 is to be used. How many boys from year 7 should be in the sample?**Age Range (years)**Age Range (years) No of Males No of Males No of Females No of Females Under 30 5400 4800 Under 40 6400 7600 30 or over 12500 11100 40 or over 11500 12100 Example Question 3: There are 37,600 people in a town who can vote in a local election. They are categorised by age and gender as shown in the table below. A market research company intends to take a survey of the voting intentions of 1800 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Female aged under 40 (b) Male (c) Aged 40 or over Question 4: A town in a different part of the country has 33 800 people who are eligible to vote . They are categorised by age and gender as shown below. A different market research company intends to take a survey of the voting intentions of 2500 residents just prior to the election. Calculate the number of people in the sample that should be: (a) Male aged under 30 (b) Female (c) Aged under 30**Course - type**Course - type No of Males No of Males No of Females No of Females Full-time Full-time 1900 1900 2100 2100 Part-time Part-time 2300 2300 2700 2700 Question 5: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Males on part-time courses (b) Female (c) Full-time students Question 6: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. A sample of 400 students is to be taken to obtain their views on the quality of education that they receive. Calculate the number of students in the sample that should be: (a) Females on full-time courses (b) Male (c) Part-time students

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