Unit 7: Producing Data Mr. Evans Statistics Part 2

Focus Points Recall Population vs. Sample Define types of sampling designs

Population vs. Sample The population is the entire group of individuals that we want information about. Defined in terms of our desire of knowledge, conclusion Example: All the students in the school/ subject A sample is a part of the population that we actually examine in order to gather information. Part of which we draw conclusions Example: Grade level/ class

Other Vocab Sampling involves studying a part in order to gain information about the whole. A census attempts to contact every individual in the entire population. A carefully conducted sample is often more accurate than a census. The sample design refers to the method used to choose the sample from the population. Poor sample designs can produce misleading conclusions can produce misleading solutions

Guided Exercise #1 A sociologist wants to know the opinions of employed adult women about government funding for day care. She obtains a list of the 520 members of a local business and professional women’s club and mails a questionnaire to 100 of these women selected at random. Only 48 questionnaires are returned. What is the population of the study? What is the sample? Why?

Types of Sampling A voluntary response sample consists of people who choose themselves by responding to a general appeal. Common type of bad sample design Example: Call-in polls Convenience sampling chooses the individuals easiest to reach. Choosing people that fit a profile. Example: Mall interviews. These methods display bias, or systematic error favoring certain outcomes.