1. AP Statistics C5 D1 HW: p.285 #19-24 Quiz in 2 class days Obj: to choose a simple random sample Do Now: What is the difference between a sample and a population?

2. Chapter 5 Population – the entire group you are interested in Sample – a smaller group selected from the population

3. Notation Parameters (Describe a population) Statistics (Describe a sample) Meanμ Varianceσ2σ2 s2s2 Standard Dev.σs Proportion (%)p

4. If you want to get information about a population, you could: - do a census (ask everyone in the population) - there are problems with this - very difficult to actually get to everyone - a lot of room for error OR- take a sample survey (some people from the population) - have to be very careful how you select those people

5. Possible problems with samples Bias – a sample is biased if it systematically favors one outcome over the other Convenience sample – if I want to get an idea of the SAT scores in this school, so I ask the students in my AP class what their scores were. Voluntary response sample - “How’s my driving?” bumper stickers; callers into a radio show

6. Possible problems with samples Non-response bias – people who don’t answer their phones if a calling survey is done during a weekday, people refuse to participate in a survey, don’t turn in your survey form Wording of the question bias – give your opinion in the question; ordering of answer choices

7. Simple Random Sample (SRS) This is the most common type of sample. Must be designed in such a way that: a) each individual has the same chance of being selected. b) every possible sample has the same chance of being selected. Ex: If I am going to choose a group of 2 girls and 2 boys to go to a conference, this could not be an SRS because a sample of 4 girls does not have any chance of being selected.

8. One way to create an SRS is to use a table of random digits (Table B insid the back cover of your textbook). Assign each individual in the population a number –Ex: If you have 100 people in the population, number them 00 – 99. Use your table to select a sample of size n. OR: Use your calculator: MATH  PRB  randInt(1,100,n)