No solutions required.
No solutions required.
No solutions required.
The researchers could decide which beams go into Group A and into Group B. Researchers could also allocate treatments to the groups: they could select what treatments is applied to each group of beams. This is a true experiment.
The researchers had no say in who was in hospital at the time: they could not allocate the patients to the two groups (overlay; matress). this is a quasi-experiment.
1. P: Perhaps people in a suburb of the Sunshine Coast; O: number of doctor’s visits in the next six months; C: between people owning a pet for those six months, and those who do not own a pet for those six months. 2. For an experiment, we would need to intervene to give subjects a pet, or not give them a pet. 3. For an observational study, we would not intervene: We would find the subjects who already owned a pet, or who did not already own a pet.
1. P: A bit vague from this small extract: people of some kind; O: the average change in body weight over two years; C: Between the four diets; I: The diets seems to be have been imposed. 2. Experimental: The diets have been imposed by the researchers, with the intent of changing the outcome (the weight change). 3. Probably a true experiment. 4. The individuals: the diets are allocated to each individual. 5. The individuals: those from whom the weight change is taken. 6. The change in body weight over two years. 7. The type of diet.
A tricky thing here is that some books are not physically in the library, as they have been borrowed.
1. Simple random sample: A list of all the books held by the USC library is needed. This may be possible for a librarian (it may not be, and would be really huge), it certainly is not possible for a student or non-library stafff member. In principle though, number each book, and randomly select a sample from that list. 2. Stratified: Use locations (Sippy Downs; Fraser Coast; Caboolture; Gympie; Southbank; SCHI) as strata, and then a random sample of all the book in each locations. 3. Cluster: Consider each set of shelves as a cluster, and randomly select some shelves, and determine the number of pages in each book on the selected shelves. 4. Convenience: Finding books in the libraries within reach and easily accessible and on the shelves, 5. Multistage: Consider taking a random of campuses, then a random sample of the sets of shelves in the selected libraries, then selecting a random shelf from each one. then a small number of random book from each shelf. 6. Multistage perhaps.
1. Multi-stage. 2. It’s a bit like stratified… but not quite. 3. Convenience. 4. A combination of multi-stage and convenience. 5. The second last is poor, and the last is a slight improvement. The second is bit odd but is probably OK. The first might be the best.
1. Convenience, but by approaching every 10th person they are trying to make it a little more representative… but they can do a lot better. 2. Convenience, but by approaching every 5th person and going every day for a week they are trying to make it a little more representative… but they can do a lot better. 3. Self-selecting. 4. Convenience. At least the researcher is trying to get a more representative sample, by going every day for two weeks, and at different times and locations each week, and approaching someone every 15 minutes. 5. The fourth is the best, but it is still far from ‘random.’ 6. None.
A bit like cluster sampling (randomly taking a small sample from many groups, and taking everyone (or everything) in those selected groups)… but not every person in the selected schools would respond (they would decide if they responded). A combination of cluster and voluntary response sampling.
Presumably all are extraneous variables, as all are possibly related to the response variable (incidence of depression): That is why the researchers obtained this information. None can be lurking variables, as the researchers measure or observe all of them.
To be a confounding variable, the extraneous variable should be related to both the response variable (incidence of depression) and the explanatory variable (diet quality). As a result, all of the extraneous variables could potentially be confounding variables.
Response variable: something like ‘risk of developing a cancer of the digestive system.’ Explanatory variable: ‘whether or not the participants drank green tea at least three times a week.’
Lurking variable: ‘health consciousness of the participants,’ because the researchers don’t seem to have measured or observed this.
Older children would probably be more likely to be smokers, and would be larger in general: age would be a confounding variable. Age is easy to record, and usually is recorded in these types of studies, so probably not a lurking variable. (The age, height and gender of each child is recorded.)
These notes have been prepared by Amanda Shaker. The copyright for the material in these notes resides with the authors named above, with the Department of Mathematics and Statistics and with La Trobe University. Copyright in this work is vested in La Trobe University including all La Trobe University branding and naming. Unless otherwise stated, material within this work is licensed under a Creative Commons Attribution-Non Commercial-Non Derivatives License BY-NC-ND.