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.)
Discuss your answer with others in your class.
The observer effect. The researcher is directly contacting the subjects, so may unintentionally influence their responses.
1. Randomly allocate the type of water to the subject (or the order in which the subjects taste-test each drink.) 2. The subjects do not know which type of water they are drinking. 3. The person providing the water and receiving the ratings does not know which type of water they are drinking. 4. Hard to find a control. 5. Any random sampling is good, if possible.
1. Response: The amount of sunscreen used; Explanatory: The time spent on sunscreen application. 2. They were looking at potential confounding variables. 3. If the mean of both the response and explanatory variables was different for females and males, then the sex of the participant would be a confounding variable, and this would need to be factored into the analysis of the data. 4. The participants are blinded to what is happening in the study.
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.