Unformatted text preview: 3'1 Section 1.2 We learn about Populations using Samples The entities that we measure in a study are called subjects. (Usually a person or an object whose characteristics are of
interest). A characteristic being measured in a study is given the name variable. Po ulation andS m l (CD Population: The total set of subjects in which we are interested. Sample: The subset of the population for whom we have (or plan to have) data.
Ex 2: We are interested in the average age of the students in Texas Tech. With regard to this example, the entities we measure are the students. Therefore, the students are the subjects. The
characteristic being measured is the age. This is a variable in this study. The set of all the subjects of interest is the set of students in Texas Tech. Therefore the population is "students in Texas
Tech". However, it is not feasible to find the age of all the students in Texas Tech. Therefore we select a random set of students
from Texas Tech to find the average age of the group. This set of students, which we actually collect data from, is a sample. For instance, this class is could be a sample.
Descri tive St isti nd In r i l ati ti Descriptive statistics: Descriptive statistics refers to methods from summarizing the data. The summaries usually consist of graphs and
numbers such as averages and percentages. Inferential statistics: Inferential statistics refers to methods of making decisions or predictions about a population, based on data obtained
from a sample of that population. Sample statistic; and Population parameter; 0 Parameter: A numerical summary of the population
9 Statistic: A numerical summary of a sample taken from the population £15 3: Referring back to ex 2, the numerical summary we are interested in the population is the average age.
Therefore the average age of the students of Texas Tech is the parameter. The same numerical summary with regard to a sample is called a statistic. For instance, the average age ofthis class is a statistic. ...
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 Spring '08
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 Statistics

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