6.7 Quick review questions

The Giant Mine in Yellowknife, Canada, ceased operation in 1999 after operating for 50 years, during which 237,000 tonnes of arsenic trioxide was released.

One study [houben2016factors] examined the arsenic concentration in lake water from 25 lakes within a 25km radius of the mine (11 years after the mine closed), to determine if the arsenic concentration was related to the distance of the lake from the mine.

They also recorded the type of bedrock (volcanic; sedimentary; grandiorite), the ecology type (lowland; upland), the elevation of the lake (in metres), the lake area (in hectares), and the catchment area (in hectares).

1. What is the response variable?
   Arsenic concentration Distance of the lake from the mine Type of bedrock Ecology type Elevation Lake area Catchment area
2. What is the explanatory variable?
   Arsenic concentration Distance of the lake from the mine Type of bedrock Ecology type Elevation Lake area Catchment area
3. Is the variable “Catchment area” likely to be a lurking variable?
   No: It is not related to the response variable No: It is measured and recorded, so cannot be a lurking variable Yes: It may be related to the response and explanatory variables Yes: It may be related to the response variable
4. Is the variable “Type of bedrock” likely to be a confounding variable?
   No: It is not related to the response variable No: It is measured and recorded, so cannot be a confounding variable Yes: It may be related to the response and explanatory variables Yes: It may be related to the response variable
5. What is the best description of the variable “Ecology type?” Response variable Explanatory variable Confounding variable Lurking variable
6. What type of study is this?
   Experimental study, because this is a scientific study involving chemical analysis of water samples Experimental study, because the researchers need to do some laboratory work to determine the arsenic concetrations Observational study, because the researchers do not determine the distance of the lakes from the mine site Observational study, because the researchers are taking observations about the lakes (such as elevation and bedrock type)