Question

Objectives. This study aimed to clarify the relationship between community water fluoridation
(CWF) and intelligence (IQ) in New Zealand.
Methods. We conducted a study of a general population sample of those born in Dunedin, New
Zealand, between April 1, 1972, and March 30, 1973 (95.4% retention after 38 years of followup).
Residence in a CWF area, use of fluoride dentifrice and intake of 0.5milligram
fluoride
tablets were assessed in early life (prior to age 5 years); we assessed IQ repeatedly between
ages 7 to 13 years and at age 38 years.
Results. No clear differences in IQ because of fluoride exposure were noted. These findings held
after adjusting for potential confounding variables, including sex, socioeconomic status,
breastfeeding, and birth weight (as well as educational attainment for adult IQ outcomes).
Conclusions. These findings do not support the assertion that fluoride in the context of CWF
programs is neurotoxic. Associations between very high fluoride exposure and low IQ reported in
previous studies may have been affected by confounding, particularly by urban or rural status.

Which epidemiologic study design is described above?

In examining the association between an exposure and outcome, which of the following is true
about a confounding variable? (Select ALL)
a. A confounder is a result of the exposure.
b. A confounder is not a risk factor of the outcome of interest.
c. A confounder alters the observed association between the exposure and outcome.
d. A confounder is associated with the exposure of interest.

To develop Disease Z, an individual must have been exposed to environmental toxin A.
Some individuals exposed to environmental toxin A, though, will not develop Disease Z.
Based on the above information, environmental toxin A is ________ for developing Disease Z:
a. Necessary and sufficient
b. Necessary but not sufficient
c. Not necessary and not sufficient
d. Not necessary but sufficient

Which of the following is true for simultaneous testing? (Select one)
a. Net specificity is greater than the specificity of either test alone
b. Net specificity is less than the specificity of either test alone
c. Net specificity is the same as that of the more specific test
d. Net specificity is the same as that of the less specific test

Answer 1

The above study is a case control study design.

The case control is a type of epidemiological observational study. An observational study is a study in which subjects are not randomized to the exposed or unexposed groups, rather the subjects are observed in order to determine both their exposure and their outcome status and the exposure status is thus not determined by the researcher.

In statistics, a confounder (also confoundingvariable, confounding factor, or lurking variable) is a variable that influences both the dependent variable and independent variable causing a spurious association

A confounding variable is an outside influence that changes the effect of a dependent and independent variable. This extraneous influence is used to influence the outcome of an experimental design.Confounding variables can ruin anexperiment and produce useless results

1.a)A confounder is a result of the exposure.

c)A confounder alters the observed association between the exposure and outcome.

d)A confounder is associated with the exposure of interest.

A necessary condition is a condition that must be present for an event to occur. A sufficient conditionis a condition or set of conditions that will produce the event. A necessary condition must be there, but it alone does not provide sufficient cause for the occurrence of the event.

2.b)Necessary but not sufficient

In simultaneous testing, net sensitivity increases and net specificity decreases with each additional test.

3. a)In simultaneous testing net specificity is greater than the specificity of either test alone