ObserveDevelop Theory/ Hypothesis TestCollect & Conclude Lesson 9 – Understand issues with sampling and generalisability. Sampling Techniques

People in Ruislip High Street are approached to take part in a study on shopping behaviour. An poster in placed in the library asking for students to take part in a memory study. A researcher visits a day care centre and asks parents to help with an investigation into the effects of day care. A psychologist uses his research methods class students to fill out a questionnaire on their revision habits.

Mr Griffin uses some of his psychology class for a study and selects them using his powerpoint name selector. A psychologist researches year 7 Ruislip High school students. He chooses 50 by cutting up names from the register and picking them from a hat. A researcher visits a day care centre and asks parents to help with an investigation into the effects of day care. A researcher conducts a study in a business with 100 workers. He has 50 short straws and 50 longer straws. He asks them all to select one…. Those who select the short straws take part in the study.

General Population = Everyone Target population = people the research is interested in E.g. males E.g. children who go to day care Sample – those from the target population who take part in the study Sampling technique – how the sample was chosen: random, opportunity, or volunteer Is the sample Representative?

General Population = everyone Target population = people we are are interested in Sample = who from the target population you test/observe/give questionnaire to Sampling technique = how you get the sample But does that sample represent the target population? ObserveDevelop Theory/ Hypothesis TestCollect & Conclude Recap

Sampling Techniques Random Equal chance so unbiased. More representative Often not possible. Quick, easy, more practical Sample influenced by where people asked- generally unrepresentative More varied sample. Volunteer bias (e.g. more motivated). May not be typical of the target population- unrepresentative

Identify the sampling technique used in this study (1 mark) Explain one strength and one weakness of using this technique in this study (2 + 2 marks). –‘ in this context’ – ‘for the researchers’ –‘ in this investigation’ One strength of this technique is…. (knowledge) In this study…. (application) One weakness of this technique is…. (knowledge) In this study…. (application) Exam technique Task: 1.Sampling technique? 2.One strength/ weakness is…. 3.In this situation…. Task: 1.Sampling technique? 2.One strength/ weakness is…. 3.In this situation….

Random technique, + and – Opportunity technique, + and – Volunterre technique, + and – ObserveDevelop Theory/ Hypothesis TestCollect & Conclude Sample Revision 1. Advert in a newspaper 2. Sample bias - the eventual pp’s may be more motivated which is why they signed up 3. Narrow sample – depending on where people are asked. 4. Often not practical/possible 5. Go to a day care centre and ask for pp’s 6. More varied sample as can reach more people. 7. Unbiased sample due to equal chance of being selected. 8. Quick/easy and practical 9. Pick names out of a hat