Questions:

1. Would you classify consecutive week or consecutive day sampling as bad sampling? If yes, what kind is it (i.e., convenience, biased, voluntary response, or all)?

2. If it is bad sampling, how can it affect empirical results?

3. How could this influence voters?

4. Would you consider using surveys to gather opinions instead of randomly sampling opinions (like re-tweets, comments, etc.) on social media platforms? EXPLAIN if you choose "YES" or "NO"

5. List the potential limitations in using sample surveys.

The Basic Practice of Statistics Ninth Edition David S. Moore William I. Notz Chapter 8 Producing Data: Sampling Lecture Slides 2021 W. H. Freeman and CompanyIn Chapter 8, we cover 0 Population versus sample - How to sample badly 0 Simple random samples - Inference about the population 0 Other sampling designs - Cautions about sample surveys - The impact of technology ' ' nference about the population 0 The purpose of a sample is to give us information about a larger population. 0 The process of drawing conclusions about a population on the basis of sample data is called inference. - Why should we rely on random sampling? 1. To eliminate bias in selecting samples from the list of available individuals. 2. The laws of probability allow trustworthy inference about the population. . Results from random samples come with a margin of error that sets bounds on the size of the likely error. . Larger random samples give better information about the population than smaller samples. Other sampling designs . The basic idea of sampling is straightforward: Take an SRS from the population, and use your sample results to gain information about the population. Sometimes there are statistical advantages to using more complex sampling methods. . For example, one common alternative to an SRS involves sampling important groups (called strata) within the population separately These "sub-samples" are combined to form one stratified random sample. . To select a stratified random sample, first classify the population into groups of similar individuals, called strata. Then choose a separate SRS in each stratum, and combine these SRSs to form the full sample. . Another example is multistage samples.Cautions about sample surveys - Good sampling technique includes the art of reducing all sources of error. - Under-coverage occurs when some groups in the population are left out of the process of choosing the sample. - Nonresponse occurs when an individual chosen for the sample can't be contacted or refuses to participate. - A systematic pattern of incorrect responses in a sample survey leads to response bias. - Wording effects are the most important influence on the answers given to a sample survey. Impact of technology . The expense of using personal interviews to do surveys has led to most studies being conducted with technology- based data collection. Issues . Random-digit dialing has grown less useful, because call screening is now nearly universally practiced and the proportion of homes with no landline has increased. . Web surveys are used more frequently but are difficult to do well./'\\-, Watch for these points: 0 A sound statistical design is necessary it we are to trust data from a sample for drawing sound conclusions about the population. 0 When sampling from large human populations, even with a sound design, there are still many \"practical difficulties\" that arise. - The impact of technology (particularly cell phones and the Internet) is making it harder to produce trustworthy national data by sampling. Population versus sample . The distinction between population and sample is basic to statistics. To make sense of any sample result, you must know what population the sample represents. . The population in a statistical study is the entire group of individuals about which we want information. . A sample is the part of the population from which we actually collect information. We use information from a sample to draw conclusions about the entire population. . A sampling design describes exactly how to choose a sample from the population. . The first step in planning a sample survey is to say exactly what population we want to describe. . The second step is to say exactly what we want to measure that is, to give exact definitions of our variables.Sample survey example The most important government sample survey in the United States is the monthly Current Population Survey (CPS) conducted by the Bureau of the Census for the Bureau of Labor Statistics. The CPS contacts about 60,000 households each month. An official website united States Depar ent of Labor Follow Us | Release Calendar | Blog U.S. BUREAU OF LABOR STATISTICS Q Search BLS.gov HOME * SUBJECTS * DATA TOOLS " PUBLICATIONS V ECONOMIC RELEASES V STUDENTS V BETA Labor Force Statistics from the Current Population Survey CPS a PRINT: BROWSE CPS The Current Population Survey (CPS) is a monthly survey of households conducted by the LATEST NUMBERS CPS HOME Bureau of Census for the Bureau of Labor Statistics. It provides a comprehensive body of data on the SEASONALLY ADJUSTED CPS OVERVIEW labor force, employment, unemployment, persons not in the labor force, hours of work, earnings, and other demographic and labor force characteristics. Unemployment Rate: CPS NEWS RELEASES 4.4% in Mar 2020 CPS DATABASES Change in Unemployment Level: CPS TABLES Announcement +1,353,000 in Mar 2020 CPS PUBLICATIONS The impact of the coronavirus (COVID-19)_pandemic on the Employment Situation for March 2020 Change in Employment Level: 2,987,000 in Mar 2020 CPS FAQS Change in Civilian Labor Force CONTACT OPS Level: For Your Information -1,633,000 in Mar 2020 SEARCH CPS "> Seasonally adjusted data for veterans and nonveterans Civilian Labor Force Participation > Charting the labor market: a chart package with the latest Current Population Survey data Rate: CPS TOPICS 62.7%% in Mar 2020 Employment-Population Ratio: CPS TOPICS A TOZ 60.0% in Mar 2020 DEMOGRAPHICS Next Releases: EMPLOYMENT ANNUAL AVERAGES UNEMPLOYMENT The Employment Situation for April 2020 is scheduled to be released on May 8, 2020, at 8:30 A.M. Unemployment Rate: Eastern Time. 3.7% for 2019 EARNINGS Unemployment Level: HOURS OF WORK 6,001,000 for 2019 TECHNICAL DOCUMENTATION On This Page 2historical Data News Reisase RELATED LINKS CPS News Releases "> CPS FAQS NFORMATION FOR CPS PARTICIPANTS 1 CPS Databases CPS Special Notices SUBSCRIBE CPS Publications CPS Related Links STATE AND LOCAL LABOR Subscribe to receive from BLS FORCE DATA CPS Tables Contact CPS Economic News Release e-mail. NONFARM PAYROLLHow to sample badly A sample selected by taking the members of the population that are easiest to reach is called a convenience sample. . The design of a sample is biased if it systematically favors certain outcomes. . Caution: People who take the trouble to respond to an open invitation are usually not representative of any clearly defined population. . A voluntary response sample consists of people who choose themselves by responding to a general appeal. Voluntary response samples show bias, because people with strong opinions are most likely to respond.to choose an SR3 - Atable of random digits is a long string of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 with these properties: . Each entry in the table is equally likely to be any of these 10 digits. . The entries are independent of each other. That is, knowledge of one part of the table gives no information about any other part. Using Table B to choose an SRS 0 Step 1: Label. Give each member of the population a numerical label of the same length. 0 Step 2: Table. Read consecutive groups of digits of the appropriate length from Table B. Your sample contains the individuals whose labels you find. SRS example (1 of 2) Use the random digits provided to select an SRS of four hotels. 01 Aloha Kai 08 Captiva 15 Palm Tree 22 Sea Shell 02 Anchor Down 09 Casa del Mar 16 Radisson 23 Silver Beach 03 Banana Bay 10 Coconuts 17 Ramada 24 Sunset Beach 04 Banyan Tree 11 Diplomat 18 Sandpiper 25 Tradewinds 05 Beach Castle 12 Holiday Inn 19 Sea Castle 26 Tropical Breeze 06 Best Western 13 Lime Tree 20 Sea Club 27 Tropical Shores 07 Cabana 14 Outrigger 21 Sea Grape 28 Veranda 69051 64817 87174 09517 84534 06489 87201 97245 69 05 16 48 17 87 17 40 95 17 84 53 40 64 (89 20 Our SRS of four hotels is 05 Beach Castle, 16 Radisson, 17 Ramada, and 20 Sea Club.SRS example (2 of 2) Using technology to select an SRS of four hotels. 01 Aloha Kai 08 Captiva 15 Palm Tree 22 Sea Shell 02 Anchor Down 09 Casa del Mar 16 Radisson 23 Silver Beach 03 Banana Bay 10 Coconuts 17 Ramada 24 Sunset Beach 04 Banyan Tree 11 Diplomat 18 Sandpiper 25 Tradewinds 05 Beach Castle 12 Holiday Inn 19 Sea Castle 26 Tropical Breeze 06 Best Western 13 Lime Tree 20 Sea Club 27 Tropical Shores 07 Cabana 14 Outrigger 21 Sea Grape 28 Veranda Population hoppe Sample Population = 1 to 28 Select a sample of size: 4 20 16 21 10 13 14 15 17 15 19 22 23 24 SAMPLE 25 26 27 28 RESET Copy sample to clipboard Our SRS of four hotels is 10 Coconuts, 16 Radisson, 20 Sea Club, and 21 Sea Grape