SECTION 1 CHAPTER 1

DATA What is Statistics? The science of collecting, organizing, and interpreting numerical facts, which we call data Data (def.) – the numbers or information collected in a study or experiment.

MEASUREMENTS Measurements are made on individuals and organized in variables. Individuals are objects described by data, can be people, animals or things. Variables are the characteristics of an individual. A variable can take different values for different individuals.

EXAMPLE Political party preference in the United Sates depends in part on age, income, and the gender of the voter. A political scientist selects a large sample of registered voters. For each voter, she records gender, age, household income, and whether they voted for the Democratic or Republican candidate in the last congressional election. What are the individuals in this situation? And, what are the variables? Individuals: Voters Variables: gender, age, household income, and whether they voted for the Democratic or Republican candidate in the last congressional election

TYPES OF VARIABLES Categorical Variable places the individual into one of the several groups or categories Quantitative Variable has a numerical value.

EXAMPLE Political party preference in the United Sates depends in part on age, income, and the gender of the voter. A political scientist selects a large sample of registered voters. For each voter, she records gender, age, household income, and whether they voted for the Democratic or Republican candidate in the last congressional election. Which variable are categorical, and which are quantitative? Categorical: Gender, political alliance Quantitative: Age, Income (gender?)

HOMEWORK Data Distribution Worksheet 1

HOW DO WE GATHER DATA? One way to gather data is to OBSERVE. The important thing to remember about observing is that you do nothing. You watch, ask. You do not influence the response. An observational study observes individuals and measures variables of interest but does not attempt to influence the responses. The purpose of an observational study is to describe some group or situations.

OTHER METHODS Sampling is gaining information about the whole by examining only a part. Observational studies that use sampling are called sample surveys. Population is the entire group of individuals about which we want information. Sample is a part of the population from which we actually collect information, which is then used to draw conclusions about the whole.

CENSUS A census is a sample survey that attempts to include the entire population in the sample. Frog Fairy Tale Correct Answer - 83

EXPERIMENT Another way to gather data is to conduct an EXPERIMENT. An experiment deliberately imposes some treatment on individuals in order to observe their responses.

HOMEWORK Data Distributions Worksheet 2