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2. Test the questionnaire on a few people first to see if it works OK or needs amending. Pilot survey: Sample Size and Type: Decide on the size and type of the sample that you intend to use. Will it be a simple random sample or a stratified random sample? Stratified Random Sampling After producing a questionnaire for your survey (see Questionnaires and Surveys) you will need to organise a sample.

3. Stratified Random Sampling can be used where the population under consideration separates naturally into sub-groups or strata. Year 7Year 8 Year 9 Year 10 Year 11 Once each of the subgroups/strata have been identified we then take a simple random sample from each one. Bilton High School

4. Stratified Random Sampling Stratified Random Sampling can be used where the population under consideration separates naturally into sub-groups or strata. Bilton High School Year 7 Year 8 Year 9 Year 10 Year 11 156 students 180 students 224 students 196 students 210 students The numbers taken in each of these samples is proportional to the size of the group.

5. Stratified Random Sampling Bilton High School Y 7Y 8Y 9Y 10Y 11 156180224196210 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

6. Stratified Random Sampling Bilton High School Y 7Y 8Y 9 156180224 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

7. Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys7084100 Girls8696124 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

8. Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys7084100 Girls8696124 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

9. Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys7084100 Girls8696124 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

10. 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. Age Range (years)No of MalesNo of Females Under 4064007600 40 or over1150012100 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

11. 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. Age Range (years)No of MalesNo of Females Under 4064007600 40 or over1150012100 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

12. 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. Age Range (years)No of MalesNo of Females Under 3054004800 30 or over1250011100 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

13. 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. Age Range (years)No of MalesNo of Females Under 3054004800 30 or over1250011100 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

14. 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. Course - typeNo of MalesNo of Females Full-time19002100 Part-time23002700 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

15. 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. Course - typeNo of MalesNo of Females Full-time19002100 Part-time23002700 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

16. 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. Course - typeNo of MalesNo of Females Full-time19002100 Part-time23002700 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

17. 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. Course - typeNo of MalesNo of Females Full-time19002100 Part-time23002700 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

18. 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. Y 7Y 8Y 9Y 10Y 11 156180224196210 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. 224180156 Y 9Y 8Y 7 Worksheets

19. 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? 124 100 Y 9 9686Girls 8470Boys Y 8Y 7 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? 124 100 Y 9 9686Girls 8470Boys Y 8Y 7

20. 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. 121001150040 or over 76006400Under 40 No of FemalesNo of MalesAge Range (years) 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. 111001250030 or over 48005400Under 30 No of FemalesNo of MalesAge Range (years) 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

21. Question 5: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender. 27002300Part-time 21001900Full-time No of FemalesNo of MalesCourse - type 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. 27002300Part-time 21001900Full-time No of FemalesNo of MalesCourse - type 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