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# Stack 2 - Sampling

### Sampling Design for AP Statistics

Question | Answer |
---|---|

The difference between an observational study and an experiment is that in the first, the explanatory variable is observed and measured, whereas in an experiment, the explanatory variable is ____. | deliberately implied |

When there is a jobs program for welfare recipients, and you simply observe that those who voluntarily take part in the program do better than those who don’t, what’s the problem with inferring that the program causes better results? | The effects of the program are confounded with the characteristics that lead people to seek the program, for example motivation and values. |

The entire group of individuals we want information about is called the _____. | population |

The subset of the population we actually examine in order to gather information is called the ______. | sample |

Studying the whole population by attempting to contact every individual is called conducting a ______. | census |

Studying a population by taking a subset of it in order to generalize to the whole population is called _____. | sampling |

The method used for selecting the sample from the population is called the ____ of sampling. | design |

If a radio station invites anyone who wants to call and give an opinion on a question, the set of people thus obtained is called a _____ response sample. | voluntary |

If the researcher enrolls a group of people in the study on the basis of how easy it is to contact them and get them to enroll, that method of sampling is called ______ sampling. | convenience |

The systematic error introduced when the sample is very different from the population is called ____. | bias |

If a conservative radio commentator polls his listeners, and a liberal commentator polls her listeners, both polls are likely to be biased as methods of ascertaining the sentiment of the country, because _______. | It’s very likely that these samples differ highly from the country as a whole. |

A SRS, or simple random sample, is a subset of n individuals from a population, chosen in such a way that ____. | Every subset of n individuals has an equal chance of being chosen for the sample. |

True or false: if every individual in the population has an equal chance of being included in the sample, the sample is a simple random sample. | False. You need not only this condition, but also that every subset of the population of size n is equally likely to be chosen. |

Suppose I take the numbers 1, 2, 3, and 4, and write them on identical pieces of paper, put them into a hat and mix them thoroughly, and draw out two numbers. Is this a simple random sample of the 4 numbers? | yes |

In a table of random digits, each triple of digits is equally likely to be any of the ____ possibilities from _____ to ______. | 1000, 000, 999 |

The two rhyming words (with different ways of spelling the second syllable) that summarize the process of using a table of random digits to select a simple random sample are ___ and ____. | Label and Table |

A sample chosen by chance is called a ____ sample | Probability |

I draw an SRS from all the girls in the class, then an SRS from all the boys in the class. This sampling method is called _______ | Stratified |

You take of SRS of all counties in the state, then an SRS of all HS in those schools and finally an SRS of students in those schools. This method is called | multistage sampling |

Sampling public HS will leave out homeschoolers. The general term for such a problem in sampling is ____. | undercoverage |

When you get a survey in the mail and immediately toss it in the trash, the source of bias this introduces into the survey is called _____. | Nonresponse. |

If you were asked what is the “essential principle of statistical sampling,” would you say that it’s to have a simple random sample, a probability sample, a stratified sample, or a multistage sample? | A probability sample, because the most essential factor is that the sample be chosen by chance |

When a survey question is leading this is called ______________ bias | wording |

Which would give more accurate results in a poll: a probability sample of 1000 people, or a voluntary response sample of 100,000 people? | The probability sample of 1000. |

A study in which we actually do something to people, animals, or objects in order to learn about the response is called an _____. | Experiment. |

The individuals on which an experiment is done are called the experimental_______? | Units |

When the experimental units are human beings, according to our book they are called ____, (although the preferred term among psychological researchers these days is “participants.”) | subjects |

The thing that is done to the subjects (or participants) (for example giving them a drug or teaching them to read) is called a ____. | treatments |

In an experiment, learning math facts is the response variable. You are studying two explanatory variables: amount of practice, and the frequency of recurrence of any one math fact in a practice session. These two explanatory variables are called the two | factors |

You are measuring the effect of temperature on baking time. You back batches of cookies at 300;350 and 375. These are | Levels of the factor Temperature |

A pill that is made of inactive material, which is used so that subjects can have information withheld about which treatment group they are in, is an example of a _____. | placebo. |

If you want evidence for causation do you choose an observation or an experiment? | experiment |

When people get better from an inactive treatment, that is called the ____ effect. | placebo |

A group of individuals who receive an inactive treatment, so that the effects of a possibly active treatment can be contrasted with those of inactive treatment, is called a ____ group. | control |

What’s the “gold standard” method of assuring the equivalence of two treatment groups? | To randomly assign subjects to treatment groups. |

The three central principles of experimental design are _____ | Control, randomization, replication |

. In a “double-blind” experiment, what two sets of people are “blind” to which group the subject is in? | The subjects themselves, and the research staff who have contact with them. |

What’s a problem in making inferences from experiments that is often less of a problem in observational studies? | The problem of “lack of realism,” in other words, the problem that the conditions in the study do not match those to which we wish to generalize. |

How do you do random assignment in a matched pairs design? | First choose pairs that are as similar as possible, then randomly choose one subject from each pair. |

. In a certain type of matched pair design where each subject serves as his or her own control, and each “pair” consists of only one individual, what is randomly assigned? | Whether the subject gets treatment 1 first or treatment 2 first. |

True or false: If we want to make separate conclusions about males and females in a study, it’s a good idea to block on gender when making our assignment to groups. | True |

Making a model that accurately reflects the experiment under consideration and imitating chance behavior based on that model is called doing a _____. | simulation |

What are the 5 steps of doing simulations? | State problem, state assumptions, assign digits to represent outcomes, simulate repetitions, state conclusions. |

You want to simulate a 30% chance of an event. You assign 0,1,2,3 to the event and the rest of the digits to the non event. Is that right? | No. You have assigned 4 numbers or 40% to the event. |