Answers to Concept Checks

• 11.1
  1. 1. How do medical errors relate to sleep deprivation of medical residents? This is a current topic of investigation and a consensus in the scientific community is still being reached. Medical residents are available for interview, and the research has very relevant outcomes.
     2. What is the average lifespan of bacteria in Martian rocks? While it is not very feasible to acquire the Martian rocks, the results would be both novel and interesting.
     3. How long does it take the Earth to complete one revolution around the Sun? This question has been asked and answered to the satisfaction of the scientific community. It is neither novel nor interesting (in terms of further research).
  2. Errors during publication of current studies adversely affect the quality of future experimentation by providing an incomplete or flawed research base. Without accurate resources, subsequent hypotheses are likely to be flawed.
  3. False. While the statement may or may not be true, this is not an easily testable hypothesis. While not required, if–then formatting of a hypothesis necessarily implies a testable relationship between ideas.
• 11.2
  1. This experiment would likely have inaccuracy error but not imprecision error. In other words, the scale would reliably read the same mass or weight, but the mass or weight it reads is not correct. This would lead to bias in the results.

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  3. Controls in experiments help to establish causality by demonstrating that the outcome does not occur in the absence of an intervention. Controls are used to keep the manipulations of different systems as similar as possible, or as a known standard against which to judge an experimental manipulation. Without controls, it is far more difficult to establish causality.
• 11.3
  1. False. Temporality is the only necessary criterion from Hill’s criteria. If temporality is not satisfied, the relationship cannot be said to be causal. The addition of other criteria increases the probability of a causal relationship, assuming that temporality has not been invalidated.
  2. Observational research does not involve manipulation of the subjects’ environment. It is generally less conclusive and more subjective than experimental research, which does involve manipulation of the subject or environment.
  3. Bias is a systematic (unidirectional) error that occurs during the selection of subjects or the measurement and collection of data. Confounding is an error that occurs during data analysis, in which an association is erroneously drawn between two variables because of a shared connection to a third variable.
• 11.4
  1. Autonomy is simply the right of an individual to make decisions on his or her own behalf and to have those decisions be respected. Respect for persons also requires honesty, confidentiality, informed consent, and freedom from coercion.
  2. The company is violating the principle of justice by choosing participants that are not part of the target population. The company is also introducing selection bias.
  3. The line between a coercive influence and a compensatory influence is often debated. In general, a compensatory influence is one that does not impact the decision to participate, while a coercive influence is one in which the subject loses autonomy to make the decision to participate.
  4. Children, pregnant women, and prisoners are considered especially at risk for coercion and thus are granted special protections.
• 11.5
  1. Internal validity is the tendency of the same experiment to produce the same results when repeated, and provides support for causality. External validity is the ability to take the information generated during research and apply it to a larger group. External validity is also called generalizability.
  2. Small samples are subject to more random variation than large samples. If only one person is selected, he or she may be an outlier, but if a much larger sample is selected, an outlier will have less of an effect on the results.
  3. A study must have both statistical significance and clinical significance to provide justification for an intervention. A study without statistical significance may be the result of random chance, whereas one without clinical significance will not impact patients.