Week 5 Sampling

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1. As a part of their customer-service program, United Airlines wanted to select 10 passengers from today's 9 A.M. Chicago-Tampa flight to be interviewed regarding airport facilities, service, and amenities in the waiting area. Each passenger was given a number on check in, starting with 001 and ending with 250. a. Describe how you would take a systematic sample of 10 passengers. ANSWER: Systematic sampling is a procedure in which an initial starting point is selected by a random process and then every nth number on the list is selected. In the case of the problem at hand, the 10 passengers who will be used as respondents will be identified using the following steps: 1. Make use of the prepared listing of the passengers who were given a number when they checked in. In the example it would be 001 to 250. 2. Compute the skip interval by dividing the total number of names in the list by the sample size: Skip interval = 250/10 = every 25th name in the list 3. Use random numbers to determine the first number that must be the start of the sampling list. The table of random numbers is a listing that is basically generated electronically (from 001 to 250) where no duplication of number is ensured. If from the randomly listed numbers, 9 was selected (or picked), the first sample is passenger number 009. The next samples would be every 25th number after the starting position which is 9; until all the 10 desired samples were determined. 4. Treat the list as circular. When the last number has been reached but the desired samples has not been determined, the counting of the skip interval may proceed to the first number until the sample size is determined. b. Describe how you would take a cluster sample of 10 passengers. ANSWER: Cluster sampling is also one of the probability sampling techniques in which members of the population (or all the 250

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