E.2 Answers to Lecture 2 tutorial
E.2.1 Answers to Sect. 2.1
Answers implied by the crossword.
E.2.2 Answers to Sect. 2.2
- Outcome: mortality rate or similar; Response variable: whether or not an individual baby survived.
- Comparison: Between home and hospital births; Explanatory variable: Where the baby is born (this is what varies)
- Observational (retrospective) study.
- Some are up for debate…
The point here is that confounding variables
are (potentially) related to both the response and explanatory variables.
- The maximum temperature on the day of giving birth: Neither? Possibly confounding?
- The health of the mother; Confounding (and hence extraneous, according to our definitions).
- The distance to the nearest hospital: Confounding (and hence extraneous, according to our definitions).
- The number of previous births by the mother: Not sure. Possibly confounding. I’d have to think more.
- Baby’s gender: Probably neither. Related to mortality (male babies have higher infant mortality) but not to the place of birth.
- Not experimental.
- Observational (retrospective) study.
- Possible RQ: “Among American mothers’ births (P), is the neo-mortality rate (O) the same when giving birth at home compared to giving birth in hospital (C)?”
- Cause-and-effect not reasonable (observational study).
- Voluntary response. Data volunteered are likely to be more favourable than the data that was not volunteered. Limitations: many. For example, mothers who have been told to expect a difficult birth would probably opt for an in-hospital birth.
- This report doesn’t suggest it is safer.
- The headline is acccurate, but is certainly not the complete story as it implies cause-and-effect.
E.2.3 Answers to Sect. 2.3
This may be on hold during COVID-19… Unless someone has a great idea.
The purpose of this question is to get them thinking about Assessment Task 2A, and design issues in particular. There are many correct answers, and experiments and observational studies are both possible.
You could show the Project Proposal form on the overhead screen, and get the students to work through it one page at a time.
This week, we plan a study that we will continue next week (i.e. collect the data). The whole class will do the same study, and contribute data.
I will compare the reaction time for students: Use each students dominant and non-dominant hand. This is a descriptive RQ, so not suitable for their project, but we still get to discuss many design features (the main purpose). To begin, state that we will compare left-hand reaction ‘time’ to right-hand reaction ‘time’. This is not the best idea, as some people and left-handed and some are right-handed. Better is to compare dominant and non-dominant hands. You can lead a discussion that encourages students to come to this realisation.
Initially tell them what you want in general terms, and tell them to Go! They’ll probably all start measuring without any planning. So let them go for one or two minutes, then pull them up and start ranting and raving: What about the planning process!? Even observe and then tell the student how different groups were doing things differently to make your point.
Then have the students discuss each planning component as a class. Form a class consensus on how to proceed, and keep a record of what the class decides. You will actually do this study in following weeks, so also be practical! You may like to prepare a Word document with this info (during class time), then over the following weeks as we compile more about the study (e.g. numerical and graphical summaries) add to this Word document.
You can use the Proposal Pro Forma even.
Be careful. The unit of analysis is the person, and each person gets two units of observation. Remember: jamovi and SPSS like data arranged with one unit of analysis (i.e. person in this case) per row.We can measure reaction ‘time’ by dropping a ruler placed at 0cm between the open fingers of a person (a given distance apart), and when it is dropped the person catches it. Measure the reaction ‘distance’ by the measurement on the ruler. But other things are possible…
E.2.4 Answers to Sect. 2.4
- 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”.
- It has: “the type of oil was known only by the food scientist…”
- “the type of oil was known only by the food scientist…”