Statistics & Research

General Background Importance of Statistics Importance of Statistics –Numbers are powerful –Understanding research –Conducting research Software Software –SPSS –Excel

Variables Variable – something that can take on more than one value Variable – something that can take on more than one value Independent variable – explains or causes Independent variable – explains or causes Dependent variable explained or effect Dependent variable explained or effect

Examples of Variables Example Example –Sex –Eye color –Class standing –Age –Height –Weight –Visualization –SAT-Verbal –Curiosity Possible values Possible values –Female, male –Blue, brown, green –Fr, soph, jr., sr. –6, 19, 25, 70 (years) –60, 72, 84 (inches) –79, 101, 220 (lbs) –1.5, 2.0, 3.0 (secs) –500, 600 (scores) –40, 50, 60 (scores)

Population & Sample Population – the complete collection; everyone of interest (adults in U.S.; students at USF) Population – the complete collection; everyone of interest (adults in U.S.; students at USF) Sample – a subset of the population (students at USF are a sample of adults in U.S.; student in this class are a sample of students at USF). We usually do research with a sample. Quick and cheap. Using the population is too costly. Sample – a subset of the population (students at USF are a sample of adults in U.S.; student in this class are a sample of students at USF). We usually do research with a sample. Quick and cheap. Using the population is too costly.

Parameter & Statistic Parameter – a numerical summary of the population (average age of students at USF if students at USF is the population). Parameter – a numerical summary of the population (average age of students at USF if students at USF is the population). Statistic – a numerical summary of a sample (average age of students in this class if students at USF is the population). Statistic – a numerical summary of a sample (average age of students in this class if students at USF is the population). Sample statistics serve 2 purposes: Sample statistics serve 2 purposes: –Descriptive –Inferential

Relations among Terms Sample 10 people 10 peoplePopulation all adults in U.S. all adults in U.S. Statistic mean meanParameter Symbol English (Arabic) M or Greek(mu)

Review Definitions Population Population Sample Sample Parameter Parameter Statistic Statistic

Types of Studies Design – set of data collection procedures Design – set of data collection procedures Experiment (Experimental study) Experiment (Experimental study) –IV manipulated; often random assignment Correlational study Correlational study –IV measured, not manipulated

Experiment Independent Variable Independent Variable –schedule Dependent Variable Dependent Variable –Rph Extraneous Variable(s) Extraneous Variable(s) –Sex of experimenter –marble

Another Example Brannick wants to know if beer consumption the night before an exam is related to exam scores the following day. He asks each student taking an exam the number of beers they had the night before and calculates the total score to see relationship. Brannick wants to know if beer consumption the night before an exam is related to exam scores the following day. He asks each student taking an exam the number of beers they had the night before and calculates the total score to see relationship. Experimental or correlational? Experimental or correlational? IV? DV? Extraneous (nuisance)? IV? DV? Extraneous (nuisance)?

Definition The way in which a study is set up and conducted is known as the study’s The way in which a study is set up and conducted is known as the study’s –Conduct –Design –Operation –Transport

Definition In an experimental study, the ___________ variable is usually deliberately manipulated. In an experimental study, the ___________ variable is usually deliberately manipulated. –Dependent –Extraneous –Independent –Nuisance

Definition We want to know about a large group of people, but we can only afford to study a small group of people. In statistics, the larger group is called the We want to know about a large group of people, but we can only afford to study a small group of people. In statistics, the larger group is called the –Focus –Generalization –Population –Sample