Population and Sampling

You walk up to this place ________________________. Then walk into the door ands smell so many sweet delicious scents. Then you look in the glass and discover all the delicious flavors Mmmm they all look so delicious So what should you do to decide what flavor you might want? Get a sample What is a sample? It is like a little taste of what you might want or are looking for

Sampling demonstration Directions: Your going to taste 3 different Jelly Beans and pick which one you like the best. If you don’t want to test the Jelly Beans then you can pick the color you like the best. Have students try a jelly bean and guess the flavor? Directions: Your going to taste 3 different Jelly Beans and pick which one you like the best. If you don’t want to test the Jelly Beans then you can pick the color you like the best. Which Jelly Bean did you like best? Do you think this represents the whole population of the class? School? Nuevo?

Today I am: Going to understand that _____________ can be used to gain information about a _________________ by examining a ____________ of the population; generalizations about a population from a sample are valid only if the sample is representative of that population. Understand that random sampling tends to produce representative samples and support valid inferences. So that I can: Use a _____________________ to draw inferences about a population by explaining how statistics can be used to gain information about a population by examining a sample of the _______________________. I’ll know if I got it if: I can judge a _________________ and _________________ if it represents that population. statistics population sample random sample population sample identify

Population Definition: the group of interest

Sample Definition: data collected for analysis

Sampling Definition: collecting data from a subset of data

Data Definition: information collected for observation or analysis

Representative Sampling Definition: in data collection, a sample whose values are represented of the whole population

Random Sampling Definition: data collected from a subset of a population that is chosen randomly

Biased Sampling Definition: A sample is biased if individuals or groups from the population are not represented in the sample.

Inference Definition: an informed guess based on evidence

Problem 1 A factory manager wants to know how many of the 20,000 LED light bulbs made each day are defective. His employees suggest three possible ways for taking a sample of 200 bulbs: Method 1: Test the first two hundred bulbs made each day. Method 2: Test every one hundredth bulb made each day. Method 3: Assign the numbers 1 to 20,000 to the bulbs. Randomly select 200 numbers between 1 and 20,000, and test the bulbs with those numbers. Which method will allow the manager to make the best guess of the total number of defective bulbs made each day?

Problem 2 Reggie wants to find out the favorite website of the 700 students in grades 7 though 9. His plan for taking a sample it to ask the first 20 male 8th graders on his school bus to name their favorite website: a. Describe a better sampling method that Reggie can use. b. Do you think if he takes two random samples of the same size, he will get the same results?

Problem 3 In Ancient West Africa, salt and gold were very valuable. Would it be a true statement to say: Everyone in West Africa was wealthy from the abundance of salt and gold ? a. Do you think this is an accurate statement? b. What might be a better statement?

Problem 4 Nuevo citizens patrol wants to know if the town’s residents are in favor of putting speed bumps on residential streets in Nuevo. On a Tuesday around noon, they knocked on the doors of fifty residents in one neighborhood to ask, “Would you like speed bumps on your street to slow drivers down?” a. Do you think the opinions they get are likely to represent those of all residents in Nuevo? b. Create 2 other methods that might be better to represent the community of Nuevo.

Re-visit Objective Tell you group how you can now: judge a sample and identify if it represents that population.

Homework Page 270 #’s 1-3