PART I SUMMARY

Here are the most important skills you should have acquired after reading Chapters 1 to 9.

  1. A. DATA

    1. 1. Recognize the individuals and variables in a statistical study.

    2. 2. Distinguish observational from experimental studies.

    3. 3. Identify sample surveys, censuses, and experiments.

  2. B. SAMPLING

    1. 1. Identify the population in a sampling situation.

    2. 2. Recognize bias due to voluntary response samples and other inferior sampling methods.

    3. 3. Use Table A of random digits to select a simple random sample (SRS) from a population.

    4. 4. Explain how sample surveys deal with bias and variability in their conclusions. Explain in simple language what the margin of error for a sample survey result tells us and what “95% confidence’’ means.

    5. 5. Use the quick method to get an approximate margin of error for 95% confidence.

    6. 6. Understand the distinction between sampling errors and nonsampling errors. Recognize the presence of undercoverage and nonresponse as sources of error in a sample survey. Recognize the effect of the wording of questions on the responses.

    7. 7. Use random digits to select a stratified random sample from a population when the strata are identified.

  3. C. EXPERIMENTS

    1. 1. Explain the differences between observational studies and experiments.

      205

    2. 2. Identify the explanatory variables, treatments, response variables, and subjects in an experiment.

    3. 3. Recognize bias due to confounding of explanatory variables with lurking variables in either an observational study or an experiment.

    4. 4. Outline the design of a completely randomized experiment using a diagram like that in Figure I.2. Such a diagram should show the sizes of the groups, the specific treatments, and the response variable.

    5. 5. Use random digits to carry out the random assignment of subjects to groups in a completely randomized experiment.

    6. 6. Make use of matched pairs or block designs when appropriate.

    7. 7. Recognize the placebo effect.

    8. 8. Recognize when the double-blind technique should be used.

    9. 9. Be aware of weaknesses in an experiment, especially in the ability to generalize its conclusions.

    10. 10. Explain why a randomized comparative experiment can give good evidence for cause-and-effect relationships.

    11. 11. Explain the meaning of statistical significance.

  4. D. OTHER TOPICS

    1. 1. Explain the three first principles of data ethics (protect subjects from harm, informed consent, and confidentiality). Discuss how they might apply in specific settings.

    2. 2. Explain how measuring leads to clearly defined variables in specific settings.

    3. 3. Evaluate the validity of a variable as a measure of a given characteristic, including predictive validity.

    4. 4. Explain how to reduce bias and improve reliability in measurement.

    5. 5. Recognize inconsistent numbers, implausible numbers, numbers so good they are suspicious, and arithmetic mistakes.

    6. 6. Calculate percentage increase or decrease correctly.