Stat 20Midterm Exam, Page 2 of 1411 March 20141. In any experiment, observational study, or sample survey, the investigator must often choose betweenseveral variables to measure a quantity of interest.(a) (4 points) If an oncologist is studying the prevalence of a specific type of cancer, as a diagnostictool he or she may choose to use a blood test, an imaging study (X-Ray, MRI, CAT scan, etc.),or biopsy (minor exploratory surgery).Please pick which method you would use and givetwodistinct reasonswhy this is preferable to the other methods.(b) (3 points) Foresters need quick measurements of the size of a tree, since they must measure manytrees in a woodlot in order to assess its overall condition. Listthree distinct variablesthat aforester could use to measure the size of a tree. No explanations are necessary.