Welcome to Stat 200

Statistics Data Collection Summarizing Data Interpreting Data Drawing Conclusions from Data

Data Collection Designing experiments Observational studies Does aspirin help reduce the risk of heart attacks? Observational studies Polls - Clinton’s approval rating

Summarizing and Interpreting Data Grade distribution for a college course Baseball players batting average against left-handed pitchers during night games on artificial turf …

Drawing Conclusions Quality control and improvement Analysis of designed experiments Analysis of observational studies

Time for some definitions

Population The set of data (numerical or otherwise) corresponding to the entire collection of units about which information is sought

Population Examples Unemployment - Status of ALL employable people (employed, unemployed) in the U.S. SAT Scores - Math SAT scores of EVERY person that took the SAT during 1997 Responses of ALL currently enrolled underage college students as to whether they have consumed alcohol in the last 24 hours

Sample A subset of the population data that are actually collected in the course of a study.

Sample Examples Unemployment - Status of the 1000 employable people interviewed. SAT Scores - Math SAT scores of 20 people that took the SAT during 1997 Responses of 538 currently enrolled underage college students as to whether they have consumed alcohol in the last 24 hours

Population vs. Sample Population Sample

WHO CARES? In most studies, it is difficult to obtain information from the entire population. We rely on samples to make estimates or inferences related to the population.