Aim: Review Session 1 for Final Exploratory Data Analysis & Types of Studies HW: complete worksheet

Exploratory Data Analysis Exploratory Data Analysis: we rely heavily on plotting the data – We look for patterns that suggest interesting conclusions or questions for further study However, exploratory analysis alone can rarely provide convincing evidence for its conclusions, because striking patterns we find in data can arise from many sources

What is anecdotal data? Anecdotal evidence is based on haphazardly selected individual cases, which often come to our attention because they are striking in some way. Anecdotal data are stories; this is when people use their intuition or personal experiences as data.

How reliable is anecdotal data? Does not provide proof but may assist research efforts – These cases need not be representative of any larger group of cases. – Can provide quantitative data Can get anecdotal evidence from personal interviews, public hearings, and surveys.

What is an Experimental Study? In experiments, researchers give treatments and observe to see if they cause changes in behavior. A classic simple experiment is one in which a researcher forms two groups at random and gives each group a different treatment *Random Assignment will be spoken about in the next few class sessions*

Example of Experimental Study Fifty students were divided into groups at random. One group received math instruction via a correspondence course on the Internet. The other group was given instruction on the same math skills using a traditional textbook. The purpose was to see if instruction via the Internet was more effective than traditional textbook instruction.

Characteristics of an Experimental Study Experimental Group: the group of participants receiving the treatment – From Example: the group receiving the new type of instruction via the internet Control Group: the group not receiving treatment – From the Example: the group receiving the instruction with a textbook

What is a Nonexperimental Study? In a nonexperimental study, researchers do not give treatments; rather they observe participants in order to describe them as they naturally exist without experimental treatment – Researchers are using ways to observe participants in order to determine their attitudes, beliefs, and behaviors as they exist without experimental intervention Come in many forms – Example: surveys, interviews and questionnaires

Purpose of Experiments? The purpose of an experiment is to explore cause-and-effect relationships (i.e. treatments are given to see how they affect the participants) – ALTHOUGH nonexperimental studies can also be used for this purpose sometimes!

How can data be used? Data can be used to: 1.Describe situations or events 2.Determine whether goals are met 3.Find trends in various areas

How can data be collected? Data can be collected in various ways – One of the most common methods is through the use of surveys Surveys can be done by using a variety of methods Three common methods are – Telephone surveys – Mailed questionnaire – Personal interviews Other methods include direction observations of situations and surveying records

What are telephone surveys? Advantages: – Less costly than personal surveys – People may be more candid in their opinions since there is no face-to-face contact Disadvantages: – Some may not have phones/unlisted – May not answer calls Therefore, not all people have a chance of being surveyed – The tone of the interviewers voice may influence the response of people who are being interviewed

What are questionnaire surveys? Advantage: – Used to cover a wider geographic area – Less expensive them all – Responses can remain anonymous if desired Disadvantages: – Low number of response and inappropriate answer to questions – Some may have difficultly reading, understanding and/or interpreting the questions

What are personal interview surveys? Advantage: – Obtaining in-depth responses Disadvantages: – Interviewer must be trained in asking questions and recording responses – More costly than the others – The interviewer may be biased in his/her selection of people to interview

Samples Researchers use samples to collect data and information about a particular variable from large population Using samples save time and money It also may enable the research to get more detailed information about a particular subject

Choosing a sample Samples cannot be chosen in a haphazard way because the information obtained may be biased – Example: interviewing people on a street corner during the day would not include responses from people working in offices at that time or those in school To obtain unbiased samples, statisticians use four basic methods of sampling: – Random Sampling – Systematic Sampling – Stratified Sampling – Cluster Sampling

What are the four basic methods of sampling? 1.Random Sampling: selected by using chance methods or random numbers 2.Systematic Sampling: numbering each subject of the population and then selecting every kth subject 3.Stratified Sampling: dividing the population into groups according to some characteristic that is important to the study, then sampling from each group 4.Cluster Sampling: the population is divided into groups called clusters by some means such as geographic area or schools in large school districts, etc. Then the researcher randomly selects some of these clusters and uses all members of the selected clusters as the subjects of the sample.

Another Methods of Sampling Convenience Sample: researchers uses subjects that are convenient – May not be representative of the population looked at but convenient for the researcher to use