Question

A recent study in Europe looked at a large group of women of childbearing age. The researchers asked each woman how much alcohol they had consumed over the past 12 months. The researchers found that women who drank moderate amounts of alcohol were somewhat less likely to have infertility than women who did not (November, 2001). The study said it “controlled for age, income and religion”.

(a) Based on the information above, was this a controlled experiment or an observational study?

(b) Why did they “control for” age, income and religion?

(c) Is this convincing evidence that infertility would decrease if women with infertility started to drink moderate amounts of alcohol? (Note: we are only asking about infertility. There may be other problems introduced by such behavior, but ignore these for answering this question).

(d) Suggest a possible confounding factor (other than age, income, or religion) and clearly explain why you think it might be a confounding factor.

Answer 1

Solution : ( a )

$\mathrm{This\:is\:an\:observational\:study\:because\:they\:did\:not\:tell\:the\:women\:how\:much\:alcohol\:they\:have\:to\:drink.}$

--------------------------------------------------------------------------------

Solution : ( b )

$\mathrm{They\:"controlled\:for"\:age,\:income\:and\:religion\:because\:these\:are\:possible\:confounding\:factors.}$

--------------------------------------------------------------------------------

Solution : ( c )

$\mathrm{No,\:because\:we\:do\:not\:know\:whether\:age,\:income\:and\:religion\:are\:confounding\:factors.\:Because}$

$\mathrm{drinking\:alcohol\:is\:associated\:with\:lower\:infertility\:does\:not\:mean\:that\:it\:casues\:lower\:infertility.}$

--------------------------------------------------------------------------------

Solution : ( d )

$\mathrm{A\:possible\:confounding\:factor\:\:\left(other\:than\:age,\:income,\:or\:religion\right)\:could\:be\:marital\:status.\:Perhaps\:singles\:}$

$\mathrm{\:drink\:more\:than\:married\:women\:and\:perhaps\:singles\:are\:less\:likely\:to\:know\:if\:they\:have\:infertility.}$