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, use a random 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; a.) Randomly b.) Systematically

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. a.) Randomly b.) Systematically

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.