A.2 Answer: TW 2 tutorial

Answers for Sect. 2.2

  1. Read the Guidelines carefully to find out!
  2. The study is observational, but because the researchers cannot determine the C (whether the person is a smoker or not). The critical element here is C, not O.
  3. This is a mix of both C ('smokers and non-smokers') and O ('the median serum cholesterol').
  4. External validity only refers to whether the sample represents the given target population, which is Australians. Whether the results apply for the entire world is irrelevant.
  5. "Serum cholesterol" is not a variable; nothing here is varying. "Serum cholesterol" is just a type of cholesterol.
    What actually varies--and so is the variable--is "the serum cholesterol concentration", or the "value of serum cholesterol".
  6. This is not an experiment, since the individuals cannot be directed into the comparison groups (between smokers and non-smokers) by the researchers.
  7. In the data file, each row is a unit of analysis and each column is a variable. So there will be two variables but not those listed: one column will record the smoking status (Yes/No) and one column will record the serum cholesterol concentration.
  8. A confounding variable has to be related to both the response and explanatory variables.
  9. The observer effect is about how the researchers might respond, not the individuals under study.

Answers for Sect. 2.3

The answers are, in alphabetical order: beach; blind; control; ethical; experimental; fire; Hawthorne; help; nominal; randomly; relational; sample; three; treatment.

Answers for Sect. 2.4

  1. Outcome: average lifespan? Not sure how one measures 'ageing well'. Response variable: lifespan?
  2. Comparison: Between eating and not eating aged cheese. Explanatory variable: Whether someone eats aged cheese (or a certain amount of aged cheese) or not.
  3. Observational; but a guess.
  4. Outcome: average lifespan; response: lifespan.
  5. Comparison: Between mice drinking and not drinking spermidine; explanatory: the type of water the mice drank.
  6. Experimental; researchers treated the water.
  7. Possibly; 'aging well' is not the same as having an increased lifespan. Study is for mice, not people anyway.
  8. To act as the control group, to measure the effect of the spermidine.
  9. Outcome: average blood pressure; response: blood pressure.
  10. Probably correlational, but possibly relational.
  11. Observational.
  12. Some answers are debatable.
    1. Probably confounding (often is).
    2. Probably neither.
    3. Probably neither.
    4. Probably confounding.
    5. Probably extraneous.
  13. Not really; but 'ageing well' is very vague.
  14. No; spermidine may have an effect, but probably not due to aged cheese intake.
  15. No; observational.

Answers for Sect. 2.6

  1. Yes: 'They were randomly allocated to take palmolein ("B9") or canola ("T4") crisps for the first 3 weeks, then (without a washout period) changed over to the other type, canola or palmolein for another 2 weeks'.
  2. It has: 'the type of oil was known only by the food scientist...'
  3. 'the type of oil was known only by the food scientist...'
  4. Probably.
  5. Subjects and researchers blinded.
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