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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.

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

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 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.

Stratified Random Sampling Bilton High School Y 7Y 8Y 9Y 10Y 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

Stratified Random Sampling Bilton High School Y 7Y 8Y 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

Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys Girls 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

Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys Girls 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

Stratified Random Sampling Bilton High School Y 7Y 8Y 9 Boys Girls 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. Age Range (years)No of MalesNo of Females Under or over 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. Age Range (years)No of MalesNo of Females Under or over 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 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 or over 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 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 or over 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. Course - typeNo of MalesNo of Females Full-time Part-time 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. Course - typeNo of MalesNo of Females Full-time Part-time 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. Course - typeNo of MalesNo of Females Full-time Part-time 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. Course - typeNo of MalesNo of Females Full-time Part-time 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

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 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 9Y 8Y 7 Worksheets

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? Y Girls 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? Y Girls 8470Boys Y 8Y 7

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 or over Under 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 people who are eligible to vote. They are categorised by age and gender as shown below or over Under 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

Question 5: There are 9000 students at Stapleton College. The table below shows how the students are distributed by course-type and gender Part-time Full-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 Part-time Full-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