1. How to select and draw conclusions from samples. A population is a group of people or objects that you want to gather information about.

2. Gathering information from a sample. Self-selected sample – members of the population volunteer to participate Systematic sample – a rule is used to select members of a population such as selecting every other person. Convenience sample – easy to reach members of the population are selected. Random sample – each member of the population has an equal chance of being selected.

3. Bias in sampling Unbiased sample – representative of the population you want information about. Biased sample – some part of the population is over or underrepresented. Random samples are preferred.

4. Identify the type of sample and tell if it is biased. -A taxicab company wants to know if its customers are satisfied with the service. Each driver surveys every tenth customer during the day. -A town council wants to know if residents support having an off-leash area for dogs in the park. Eighty dog owners are surveyed at the park.

5. Margin of Error When a random sample of size n is taken from a population, the margin of error is approximated by this formula: Margin of Error =

6. Find margin of error In a survey of 1011 people 52 % said that television is their main source of news, 29% said newspapers 10 % radio, 5% internet and 4% other. -What is the margin of error for the survey? Give an interval that is likely to contain the exact percent of all people who use television as their main source of news.

7. Experiments An experiment is often conducted with two groups. One group, called the experimental group undergoes some procedure or treatment. The other group, called the control group does not undergo the procedure or treatment. In a well-designed experiment, everything else about the experimental group and the control group is as similar as possible so that the effect of the procedure or treatment can be determined.

8. Flaws in an experiment A drug company conducts an experiment to test whether a new pain relief medication is effective at relieving headaches. The experimental group consists of college students who are given the medication. The control group consists of college professors who are not given medication. The company finds that the headaches of people in the experimental group are of shorter duration than those of people in the control group. As a result, the company concludes that the medication is effective.