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Section 1.3

Section 1.3. Introduction to Experimental Design. Planning a Statistical Study. Identify individuals of interest. Specify variables, protocols, procedures. Decide on sampling method, if appropriate. Address ethics and privacy issues. Collect data.

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Section 1.3

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  1. Section 1.3 Introduction to Experimental Design

  2. Planning a Statistical Study • Identify individuals of interest. • Specify variables, protocols, procedures. • Decide on sampling method, if appropriate. • Address ethics and privacy issues. • Collect data. • Use descriptive and inferential statistics to make decisions. • Note any concerns and recommendations.

  3. Methods of Producing Data • Census • Sampling • Simulation • Experimentation • Observation

  4. Methods of Producing Data Census: Using measurements from the entire population Sampling: Draw a part of the population Simulation: Numerical facsimile of real-world phenomena Observational Study: Observations and measurements of individuals are conducted in a way that doesnot change the response or the variable being measured Experiment: A treatment is deliberately imposed on the study individuals in order to observe a possible change in the response or variable being studied.

  5. Placebo Effect A subject receives no treatment but (incorrectly) believes he or she is receiving treatment and responds favorably

  6. Randomized Two-treatment Experiment • Placebo effect is common in medical experiments. • Subjects divided into two groups. • One group receives actual treatment. • Control group receives placebo treatment disguised as real. • After treatment cycle, conditions of groups are compared.

  7. Double-blind Experiment • Neither individuals in study nor observers know which subjects are receiving actual treatment. • Helps control for subtle biases.

  8. To prevent bias or inaccurate results • Use a control group. • Assign individuals to groups randomly. • Replicate experiment many times to insure differences did not occur by chance.

  9. Lurking or Confounding Variables • Known or unknown variables that might be an underlying cause of a change in response in experimental group. • Reason for need for control group

  10. Potential Problems • Strong opinions may be over-represented if responses are voluntary. • A hidden bias may exist because of the way data is collected. • There may be hidden effects of other variables. • There is no guarantee that results can be generalized.

  11. TI-84Plus / TI-83Plus • To select a random set of integers between two specified values, • press MATH highlight PRB then press 5. • Example • RandInt (1, 100, 5) • (63 89 13 46 47) • RandInt (1, 100, 5) • (29 82 99 50 41)

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