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Unformatted text preview: What is Statistics? • Statistics is the science of collecting, summarizing, analyzing and interpreting data. • Statistics involves methods for – Designing and carrying out research studies. – Describing collected data. – Making decisions, predictions, or inferences about phenomina represented by data. Some Definitions • A Population is the entire collection of objects or outcomes about which in- formation is sought. • A Sample is a subset of a population, containing the objects or outcomes that are actually observed. • A Simple Random Sample (SRS) of size n is a sample chosen by a method in which each collection of n population items is equally likely to comprise the sample. Ex 1. A physical education professor wants to study the physical fitness level of students at her university. There are 20 , 000 students in the university and she draws a sample of size 100 to take a physical fitness test. The physical education professor obtains a list of all 20 , 000 students, numbered from 1 to 20 , 000. She uses a computer number generator to generate 100 random integers between 1 and 20 , 000. She invites the 100 students corresponding to those numbers to participate in the study. • The population of interest: 20 , 000 students in the university. • The sample: the 100 students chosen to take the physical fitness test. • The simple random sample: Yes. Ex 2. A quality inspector samples 40 bolts from a large shipment and measures the length of each to see whether they meet a length specification....
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- Spring '08