For this exercise we’re going to use a subset of the 2014 GSS. The GSS started in 1972 and has been an annual or biannual survey ever since. The GSS is a national probability sample of adults in the United States conducted by the National Opinion Research Center (NORC). We’re going to use the General Social Survey (GSS) for this exercise. PSPP will select a simple random sample for you. There are many ways of selecting a probability sample but the most basic type of probability sample is a simple random sample in which everyone in the sample has the same chance of being selected in the sample. This is a purely volunteer sample and we have no idea of the probability of selection. A show might invite you to go to a website and answer a question such as whether you favor or oppose same-sex marriage. An example of a non-probability sample is an instant poll which you hear about on radio and television shows. This isn’t the case for non-probability samples. Probability samples are samples in which every object in the population has a known, non-zero, chance of being in the sample (i.e., the probability of selection). There are many different ways to select samples. Notice that the mean age of the sample (our statistic) is known while the mean age of the population (our parameter) is usually unknown. In other words, we use the mean age of the sample to make an inference about the mean age of the population. We use statistics to make inferences about parameters. The mean age of a sample is a statistic while the mean age of the population is a parameter. So what we do is to select a sample from the population where a sample is a subset of the population and then use the sample data to make an inference about the population.Ī statistic describes a characteristic of a sample while a parameter describes a characteristic of a population. Populations are often large and it’s too costly and time consuming to carry out a complete enumeration. Another example of a population is all the students in a particular school or all college students in your state. does a complete enumeration of all individuals living in the United States every ten years (i.e., each year ending in a zero). For example, a population might be all the individuals that live in the United States at a particular point in time. Populations are the complete set of objects that we want to study. The exercise also gives you practice in using COMPARE MEANS (one-sample t test) and SELECT CASES in PSPP. The goal of this exercise is to explore hypothesis testing and the one-sample t test.
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