Types of sampling New Info Population Random Sampling All items have an equal chance of being picked. (put numbers in a hat) Systematic Sampling Systematic Sampling Make a list, roll a dice to create a starting point pick every 10 th item Stratified Sampling B B BG G Make the sample the same proportion as the population. Then select randomly from each group.

Types of sampling Question 1 Andrew wants to know what the pupils in his school think about the school meals. There are 1200 pupils in his school and he knows that he can’t talk to them all. He decides on a sample of 10% = 120. Describe how he should choose these 120 people.

Types of sampling Question 2 Alan wants to do a survey about stress at work. She decides on a sample of 1000 people. Describe how he should choose these 1000 people.

Types of sampling Question 3 A headmaster wants to sample the opinions of some of his students about afterschool clubs. The school contains 410 boys and 190 girls. The headmaster wants a sample of 50 students altogether. The deputy head suggests asking 25 boys and 25 girls, chosen at random from alphabetical lists of the boys and girls at the school. a) Explain why the sample should not contain 25 boys and 25 girls. b) Suggest a better way of taking a sample.

Types of sampling Question 4 Fred is planning to carry out a survey of 50 students at his school. He wants to see whether they like school. He decides to arrive at 7.30 am and interview the first 50 students to arrive for the day. a) Give one reason why this might not be a good sampling method. b) Describe a better sampling method that Fred might use.

Types of sampling Question 5 Explain briefly whether you think this is a good sampling method. Janice is studying the colours of sweets in tubes of Smarties. She wants to see if the different colours occur equally often. She goes to her local supermarket and buys 40 tubes. She takes them home to count the numbers of each colour.

Types of sampling Question 6 The table shows the number of students in each year group at Meadow School. There are 600 students at the school altogether. Millie wants to take a stratified sample of 50 students from the school. Draw up a table to show how many students she should select from each year group. Age group Year 7Year 8Year 9 Year 10Year 11 Number of students

Types of sampling Question 7 There are 1000 students in Nigel and Sonia’s school. Nigel is carrying out a survey of the types of food eaten at lunchtime. a) Explain how Nigel could take a random sample of students. This table shows the gender and the number of students in each year group. Sonia is carrying out a survey about how much homework students are given. She decides to take a stratified sample of 100 students from the whole school. b) Calculate how many in the stratified sample should be: (i) girls from Year 9 (ii) boys from Year 10. Year groupNumber of boys Number of girls Total

Types of sampling Question 8 A school has 450 students. Each student studies either Greek, Spanish or French. The table shows the number of students who study each language. An inspector wants to look at the work of 90 students. Use a stratified sample to work out the number of pupils studying each language that should be in the sample. LanguageNumber of students Greek 45 Spanish 121 German 98 French 186