Understanding Sampling Lesson 3-5 Pg. # Lesson 3-5 Pg. #

CA Content Standards »Statistics, Data Analysis, and Probability 2.1: I can compare different samples of a population with data from the entire population and identify a situation in which it makes sense to use a sample. »Statistics, Data Analysis, and Probability 2.4***: I can identify data that represent sampling errors and explain why the sample might be biased. »Statistics, Data Analysis, and Probability 2.1: I can compare different samples of a population with data from the entire population and identify a situation in which it makes sense to use a sample. »Statistics, Data Analysis, and Probability 2.4***: I can identify data that represent sampling errors and explain why the sample might be biased.

Vocabulary: POPULATION »The entire group of individuals or items you wish to study. »A sample is chosen from a population. »The entire group of individuals or items you wish to study. »A sample is chosen from a population.

Objective »Understand how sampling is used to describe group »Math Link: You know how to organize data and find measures of central tendency. Now you will learn how sampling is used to collect data in real-life situations. »Understand how sampling is used to describe group »Math Link: You know how to organize data and find measures of central tendency. Now you will learn how sampling is used to collect data in real-life situations. tendencies.

»Tendency: a characteristic or likelihood.

Vocabulary: POPULATION »The entire group of individuals or items you wish to study. »A sample is chosen from a population. »The entire group of individuals or items you wish to study. »A sample is chosen from a population.

Vocabulary: SAMPLE »A selected part of a large group, or population. movie

Example 1. »Jerome sells pets and supplies. He has a large barrel filled with marbles that people buy to decorate their aquariums. The marbles are various colors, all mixed together. He wonders what percent of the marbles are green.

»It does not make sense for Jerome to count all the marbles, so Jerome decided to study two samples, or parts, of the population. Remember, the population in a statistical study is the entire group of people or things being considered. In this case, the population is the entire barrel of marbles.

Sample 1. »Jerome scooped out a bucket of marbles to test. He counted 200 marbles in the bucket, 50 of which were green. 50 = 1 = 25% About 25% of the marbles in the bucket were green. »Jerome scooped out a bucket of marbles to test. He counted 200 marbles in the bucket, 50 of which were green. 50 = 1 = 25% About 25% of the marbles in the bucket were green.

Sample 2. »Jerome scooped out another bucket of marbles to test. This time he scooped out 180 marbles, 60 of which were green. 60 = 1 = 33% About 33% of the marbles in the second bucket were green. Since Jerome’s two estimates gave results of 25% and 33%, he estimated that about 30% of marbles in the barrel are green. »Jerome scooped out another bucket of marbles to test. This time he scooped out 180 marbles, 60 of which were green. 60 = 1 = 33% About 33% of the marbles in the second bucket were green. Since Jerome’s two estimates gave results of 25% and 33%, he estimated that about 30% of marbles in the barrel are green.

Example 2. »In each situation, would it make more sense to study the entire population or a sample? A.David got a new shipment of doggie treats. Each small bag is supposed to contain pieces of real beef jerky. David wants to know the average number of pieces of beef jerky per bag. It would take too much time to examine every bag. Also, after David cuts open a bag of treats, he can no longer sell it. It makes more sense to study a sample. »In each situation, would it make more sense to study the entire population or a sample? A.David got a new shipment of doggie treats. Each small bag is supposed to contain pieces of real beef jerky. David wants to know the average number of pieces of beef jerky per bag. It would take too much time to examine every bag. Also, after David cuts open a bag of treats, he can no longer sell it. It makes more sense to study a sample.

Example 2. »In each situation, would it make more sense to study the entire population or a sample? B. Kristen wants to know the average height of her cat’s new kittens. It is not difficult to measure each kitten. So, it makes more sense to study the entire population. When you interpret statistical data, it is important to know whether the statistics are based on a sample or on the entire population. »In each situation, would it make more sense to study the entire population or a sample? B. Kristen wants to know the average height of her cat’s new kittens. It is not difficult to measure each kitten. So, it makes more sense to study the entire population. When you interpret statistical data, it is important to know whether the statistics are based on a sample or on the entire population.

Example 3. »The table below shows the results of a 1999 poll of 500 dog owners in a large city. [1] Identify the population being studied. [2] Then, tell whether the statistics were drawn from a sample or from the entire population. »[1] The population is all dog owners in the city. »[2] The statistics were drawn from a sample, since not all dog owners were interviewed. »The table below shows the results of a 1999 poll of 500 dog owners in a large city. [1] Identify the population being studied. [2] Then, tell whether the statistics were drawn from a sample or from the entire population. »[1] The population is all dog owners in the city. »[2] The statistics were drawn from a sample, since not all dog owners were interviewed. Dog Owners BreedPercent Beagle35% German Shepherd30% Retriever25% Other10%

The Moral of the Story: »Studying the characteristics of a sample is a way to learn about the whole population. It is necessary to use a sample when it is impossible to study the entire population.

Name Statistics