Precision of a variable is:

Once a system becomes stable, maintenance costs usually remain low and involve minor _____ maintenance.​

Confounding can be:

Individuals are divided into sub-groups on the basis of specified characteristics  and then random samples are selected from each sub-group. This type of sampling is:

The association between smoking and dental caries has been the subject of previous epidemiological studies. Cohort studies have found no association, while at least one case-control study has found a positive association. Possible explanations for the different results in case-control and cohort studies of this topic include:

Researchers were conducting a research study to determine the clinical  attachment loss in a sample of adult smokers. The examiner who was  conducting these measurements left the University in the middle of the study.    The Principal Investigator (PI) appointed a new examiner to conduct the  remaining portion of the examinations. To assure consistency in the examinations the new examiner should be:

The investigators were assessing severity of periodontal disease among a convenience sample of older adults in the city of Rochester. They found that individuals who were African-American had much greater mean attachment loss than older adults who were Caucasian and Hispanic. To assess these differences statistically one can use:

When using multiple tests to screen for a disease, there is a loss in net sensitivity and a gain in net specificity in:

If Dr. X decides to obtain a list of all patients at Strong Memorial Hospital and  Highland Hospital and wants to select a suitable sample from this list. The best  way would be:

The Gingival Index of Löe and Silness (measured as normal, mild, moderate and  severe) is: