Lesson 30 Understanding Sampin9 Independent Practice In problem 1, follow the st

Question

Lesson 30 Understanding Sampin9 Independent Practice In problem 1, follow the steps to evaluate the proposed sampling method. 1. The owner of a department store wants to know how many visitors to her store actually make purchases. She considers three different methods for taking a sample Method 1: Ask the first hundred visitors to the store if they plan on making purchases. Method 2: Ask every 100th person who leaves the store if they made a purchase. Method 3: Call every 1,000th person on an alphabetical list of residents and ask if they usually make purchases when visiting department stores. Which, if any, of these methods is likely to produce a representative sample? a. Define the population in this situation. b. Define each proposed sample. Method 1: Method 2: Method 3: of the population? Explain. Method 1 Method 2: Method 3: 2. A factory manager wants to take a sample of 50 of the 5,000 ell phones built each day y manager wants to take a sample of 50 of the 5,000 cell phones built each day to make sure they work. Describe a sampling method that would produce a represenia sample. Why would a representative sample be useful to the manager?

Explanation / Answer

a)

The population in this situation is : All the visitors to the department store.

Whatever sampling method is used, essentially the sample is taken out from this population, which are the visitors to the store.

b)

Method 1: The sample consists of exactly 100 people. Each person in the sample will be enquired if they plan on purchasing something to which the answer will be either yes or no. The number of yes answers would give the number of visitors who purchase something for every 100 visitors.

Method 2: The number of people in this sample can vary depending on how many people visit the store in the first place. For a given day, it can be 5 if 500 people visit and 1 if 180 people visit in a day.

Method 3: The number of people in this can vary depending on how many people are in the list of residents. If there are 12,800 people, then we have 12 people, if there are 1,990 people, then we have 1 person.

c)

Method 1: This is the closest method of 3 methods to having a sample representative of the population. Then again, this is subject to a few variables as well. What if, the visitors presumably in the morning just don't buy anything and most of the purchases in the store happen mainly at night, then asking the first 100 visitors which would be in the morning will give a flawed under valued result. Also, if those 100 visitors are composed of big groups of people, say tourists, who want to purchase, then there will be a wrong result here too.  

Method 2 : This counteracts the problems faced in the Method 1. As the times of the day are neutralized and you won't ask a group of like minded people the same question, but this depends on the number of people coming to the store. What if only 450 people come to the store? Say the store caters to only a few high rise buildings in an isolated area. Then you just get the opinion of 4 people which is hardly a representative size.

Method 3 : This is the least representative of the 3 methods. The question being asked "Do you usually make purchases when visiting department stores?" This does not have a substantial link to how many of YOUR visitors buy something. Every 1000th person in the locality might purchase from some store but not from some other store. So even after getting a sufficient number of Yes or No, we still can't say if the Yes or No means anything as the question relates to a department store in general and not YOUR department store.

Cheers!

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