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INTRO TO STATISTICS MATH III LESSON 12 - 1 VOCABULARY Population • The entire group that the study is based on Sample • The part of the group being polled WHAT’S IN A SAMPLE? Random Sampling • Choosing people at random • Accurate and representative • “Every fifth person entering a grocery store is asked what their favorite radio station is.” Biased Sampling • Choosing poorly • Will influence the data • “Every fifth person entering a country music festival is asked what their favorite radio station is.” BIASED OR UNBIASED? A music store manager asks people that make purchases how many hours of music they listen to each day. A class president polls all 9th graders about their choice for a new mascot for the school. A television reporter asks people on downtown streets if they support a new project building a subway. SAMPLING A POPULATION OF 10,000 Simple Random • 100 people are randomly selected from a group of 10,000. Stratified Random • The 10,000 people are divided into non-overlapping groups, and then a random sample of each group is chosen. Systematic Random • Every 100th person in the group of 10,000 people is chosen. IDENTIFY THE TYPE OF SAMPLE • Animals in a zoo are classified by the continent they came from, and then two animals from each group are selected for blood tests. • At Burger King, the manager checks the quality of the a hamburger every 25 minutes, starting at a random time. • At a bridal shower, a sticker was placed on the bottom of three random plates. The people receiving the plates win a prize. MEASURES OF CENTRAL TENDENCY Mean (Average) • The sum of the data, divided by the number of items Median • The middle number of the ordered data Mode • The piece of data showing up the most Range • The distance between the highest and lowest value Standard Deviation • A measure of the average distance of all data points to the mean PRACTICE – MEAN, MEDIAN, MODE Find the mean, median, mode, range, and standard deviation. Test Scores #1) 86, 71, 79, 86, 79, 32, 88, 86, 82, 69, 71, 70 STANDARD DEVIATION Deviation • A measurement of how far data items are away from the mean Standard Deviation (the items) We don’t do this by hand. average deviation of all FUEL ECONOMY The table below shows the average MPG that my car used over the last 30 tanks of gasoline.