Random Sampling Homework 1.
To obtain a sample of 25 students from among the 500 students present in school today, a surveyor decides to pick every twentieth student waiting in line to attend a required assembly in the gym. a. Explain why this procedure will not result in a simple random sample of the students present that day. b. Describe a procedure that will result in a simple random sample of the students present that day. (Be specific) 2. A cable company plans to survey potential customers in a small city currently served by satellite dishes. Two sampling methods are being considered. Method A is to randomly select a sample of 25 city blocks and survey every family living on those blocks. Method B is to randomly select a sample of families from each of the five natural neighborhoods making up the city.
a. What is the statistical name for the sampling technique used in Method A, and what is a possible reason for using it rather than an SRS? b. What is the statistical name for the sampling technique used in Method B, and what is a possible reason for using it rather than an SRS? 3. A firm wants to understand the attitudes of its minority managers toward its system for assessing management performance. Below is a list of all the firms managers who are members of minority groups. Use table B starting at line 139 to choose a simple random sample of 6 to be interviewed in detail about the performance appraisal system. Agarwal Castillo Gates Kim Pliego Shen Anderson Cross Goel Liao Puri Vega Baxter Dewald Gomez Mourning Richards Wang Bonds Fernandez Hernandez Naber Rodriguez Bowman Fleming Huang Peters Santiago Random Sampling Homework 4. A furniture maker buys hardwood in large batches. The supplier is supposed to dry the wood before shipping (would that isn’t dry won’t hold its size and shape). The furniture maker chooses five pieces of wood from each batch and tests their moisture content. If any piece exceeds 12% moisture content, the entire batch is sent back. a.) Identify the population in the above setting. b.) Identify the sample in the above setting. 5. You want to take simple random sample (SRS) of 50 of the 816 students who live in a dormitory on campus. You label the students 001 to 816 in alphabetical order. In the table of random digits, you read the entries 95592 94007 69769 33547 72450 16632 81194 The first three students in your sample have labels (a) 955, 929, 400 (b) 400, 769, 769 (c) 929, 400, 769 (d) 400, 769, 335 6. A TV station wishes to obtain information on the TV viewing habits in its market area. The market area contains one city of population 170,000, another city of 70,000, and four towns of about 5000 inhabitants each. The station suspects that the viewing habits may be different in larger and smaller cities and in the rural areas. Which of the following sampling designs would give the type of information that the station requires? (A) A cluster sample using the cities and towns as clusters. (B) A convenience sample from the market area (C) A simple random sample from the whole market area (D) A stratified sample from the cities and towns in the market area 7. Bias in a sampling method is (A) any error in the sample result, that is, any deviation of the sample result from the truth about the population (B) the random error due to using chance to select a sample (C) any error due to practical difficulties such as contacting the subjects selected (D) any systematic error that tends to occur in the same direction whenever you use this sampling method 8. For your final project in AP Statistics, you decide to survey Penncrest students about their iPad usage. You label every table in the cafeteria with a number from 1-­‐65. You randomly select 5 tables and then you survey every student at each of those five tables. What type of sampling method are you using to collect your data? A) Simple Random Sample B) Stratified Sampling C) Cluster Sampling D) Systematic Random Sampling 9. Which of the following is a true statement? (A) If bias is present in a sampling procedure, it can be overcome by dramatically increasing the sample size (B) Sampling error can be eliminated only if a survey is both extremely well designed and extremely well conducted (C) Sampling error concerns natural variation between samples, is always present, and can be predicted using probability (D) Sampling error is generally larger when the sample size is larger Random Sampling Homework