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Stats Lesson 1.2 Random vs Biased Samples Notes Page 1 of 3 VOCABULARY… Population: data from every individual of interest. (Every person or thing is talked to or counted or included.) Census: measurements or observation from the entire population are used. Sample: measurements or observations from part of the population are used. Random Sample: a sample in which every person or object has an equal chance of being selected Bias Sample: a sample in which every person or object does not have an equal chance of being selected. (A biased sample, a non-random sample of a population (or non-human factors) is a sample in which all individuals, or instances, were not equally likely to have been selected.) For Examples 1 – 3, determine which would be better to use: Census or Sample Example 1: Find the average number of hours of television a person in Phoenix watches each day. Example 2: Find the average number of hours of homework each student in your math class gets each week. Example 3: Find the average age of everyone who lives in Phoenix. For Examples 4 – 7, identify whether each situation is a random or biased sample: Example 4: Determine the average annual snow fall in Colorado by measuring the snow fall in Denver. Example 5: Determine the average annual rain fall in Texas by measuring the rain fall in twenty different cities across the state. Example 6: Determine America’s favorite NBA basketball team by conducting a survey in Los Angeles. Stats Lesson 1.2 Random vs Biased Samples Notes Page 2 of 3 Example 7: Determine the most popular type of car at Moon Valley by surveying all the teachers. CALCULATOR – Mathematical Notation… ∑ is the Greek letter “Sigma”. Sigma means to find the Summation. Summation is the operation of adding a sequence of numbers; the result is their sum or total. There are many ways to do this. We will focus on two, with the calculator and without the calculator. Directions: Find the given sum. X: 4 1 4 7 5 Y: 1 8 2 1 7 Example 8: y (Solve with the calculator. List out the steps, so you can repeat the outcome with a calculator.) Example 9: Example 10: x2 2xy Stats Lesson 1.2 Random vs Biased Samples Notes Example 11: y2 x4 x y Example 12: y4 2 xy 4 4 1 xy 2 Example 13: Page 3 of 3