Get survey from Mr. Ebersole and read directions and complete it. STARTER Get survey from Mr. Ebersole and read directions and complete it.

HOMEWORK

§ 1.3 Experimental Design

Section 1.3 Objectives Discuss how to design a statistical study Discuss data collection techniques Discuss how to design an experiment Discuss sampling techniques Larson/Farber 4th ed.

Designing a Statistical Study GUIDELINES Identify the variable(s) of interest (the focus) and the population of the study. Develop a detailed plan for collecting data. If you use a sample, make sure the sample is representative of the population. Collect the data. Describe the data. Interpret the data and make decisions about the population using inferential statistics. Identify any possible errors.

Methods of Data Collection(ways to get data) In an observational study, a researcher observes and measures characteristics of interest of part of a population. In an experiment, a treatment is applied to part of a population, and responses are observed. A simulation is the use of a mathematical or physical model to reproduce the conditions of a situation or process. A survey is an investigation of one or more characteristics of a population. A census is a measurement of an entire population. A sampling is a measurement of part of a population.

Data Collection Observational study A researcher observes and measures characteristics of interest of part of a population. Researchers observed and recorded the mouthing behavior on nonfood objects of children up to three years old. (Source: Pediatric Magazine) Larson/Farber 4th ed.

Data Collection Experiment A treatment is applied to part of a population and responses are observed. Control group no treatment Placebo fake treatment An experiment was performed in which diabetics took cinnamon extract daily while a control group took none. After 40 days, the diabetics who had the cinnamon reduced their risk of heart disease while the control group experienced no change. (Source: Diabetes Care) Larson/Farber 4th ed.

Data Collection Simulation Uses a mathematical or physical model to reproduce the conditions of a situation or process. Often involves the use of computers. Automobile manufacturers use simulations with dummies to study the effects of crashes on humans. Larson/Farber 4th ed.

Data Collection Survey An investigation of one or more characteristics of a population. Commonly done by interview, mail, or telephone. A survey is conducted on a sample of female physicians to determine whether the primary reason for their career choice is financial stability. Larson/Farber 4th ed.

EXPERIMENTAL DESIGN(controlling outcomes) BIAS favor certain outcomes CONFOUNDING VARIABLE can’t tell what factors caused the outcomes PLACEBO EFFECT subject reacts favorably to a placebo HAWTHORNE EFFECT subjects change behavior because in an experiment BLIND EXPERIMENT subjects do not know if placebo or treatment DOUBLE BLIND EXPERIMENT neither experimenter or subject knows who is getting placebo or treatment REPLICATION redoing an experiment under the same conditions (do to see if was correct)

SAMPLE SIZE number of subjects in an experiment RANDOMIZATION randomly assigning subjects to different treatment groups (lots of different) SAMPLE SIZE number of subjects in an experiment

CENSUS count or measure of an entire population. SAMPLING a count or measure of a part of a population. SAMPLING ERROR difference between the results of a sample and results for a population. Example: Every student at NT takes Prob & stats.

Sampling Techniques (ways to find who to get data from) Random Sample Every member of a population has an equal chance of being selected. Simple Random Sample Every possible sample of the same size has the same chance of being selected. x Larson/Farber 4th ed.

Simple Random Sample Random numbers can be generated by a random number table, a software program or a calculator. Assign a number to each member of the population. Members of the population that correspond to these numbers become members of the sample. TI 83/84 PRB 5 MATH randInt( 1,500,4) Larson/Farber 4th ed.

Stratified Samples A stratified sample has members from each segment of a population. This ensures that each segment from the population is represented.(each group is a Strata) Freshmen Sophomores Juniors Seniors MALE FEMALE

Cluster Samples A cluster sample has all members from randomly selected segments of a population. This is used when the population falls into naturally occurring subgroups.(clusters) All members in each selected group are used. The city of Clarksville divided into city blocks.

Every fourth member is chosen. Systematic Samples A systematic sample is a sample in which each member of the population is assigned a number. A starting number is randomly selected and sample members are selected at regular intervals. Every fourth member is chosen.

Convenience Samples A convenience sample consists only of available members of the population. Example: You are doing a study to determine the number of years of education each teacher at your college has. Identify the sampling technique used if you select the samples listed. 1.) You randomly select two different departments and survey each teacher in those departments. 2.) You select only the teachers you currently have this semester. 3.) You divide the teachers up according to their department and then choose and survey some teachers in each department. Continued.

Identifying the Sampling Technique Example continued: You are doing a study to determine the number of years of education each teacher at your college has. Identify the sampling technique used if you select the samples listed. 1.) This is a cluster sample because each department is a naturally occurring subdivision. 2.) This is a convenience sample because you are using the teachers that are readily available to you. 3.) This is a stratified sample because the teachers are divided by department and some from each department are randomly selected.

Section 1.3 Summary Discussed how to design a statistical study Discussed data collection techniques Discussed how to design an experiment Discussed sampling techniques Larson/Farber 4th ed.

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ASSIGNMENT Page 23 17, 19-27, 31-36, 40,41