Question

Stadistics

1. A statistics student takes a poll at a local Starbucks to find out if they support the President’s decision for declaring the construction of a southern border wall a national emergency. He polls every fifth person that walks into the coffee shop. Why wouldnʹt this sample be representative of the entire US voting population?

2. There are many websites devoted to polling public opinion on a wide range of topics from politics to consumer preferences. Why are these biased with respect to the general U.S. population? Explain.

3. Identify the sampling technique used to obtain a sample from random, systematic, stratified or convenience sampling. Write the sampling technique in the blank provided. ______________ A group of people are classified according to the county where they live and then random samples of people from each county are taken.

______________ A lottery ball is selected out an air machine. The valve is open, balls are blown into the tube; they are then transferred through another clear tube into a display area for reading.

______________ The first 10 people to arrive at a City Council meeting are surveyed to find out their opinion on a proposed bond referendum.

______________ A quality control supervisor pulls every 20th widget off an assembly line to test for defects.

Answer 1

1) As the student polls only customers walking into the Starbucks, his sample is expected to be biased with the opinions of only a certain segment (could be upper middle class and upwards), and doesn't include the opinions of all segments of the population. Hence, it will not be representative of the entire US voting population.

2) A lot of US population might not frequently visit the politics or consumer preference related websites. There might be busy people who hardly visit such websites, much lesser so for sharing opinions. Hence,these are biased wrt the general US population.

3) Stratified sampling A group of people are classified according to the county where they live and then random samples of people from each county are taken.

Random Sampling A lottery ball is selected out an air machine. The valve is open, balls are blown into the tube; they are then transferred through another clear tube into a display area for reading.

Convenience Sampling The first 10 people to arrive at a City Council meeting are surveyed to find out their opinion on a proposed bond referendum.

Random Sampling A quality control supervisor pulls every 20th widget off an assembly line to test for defects.