Question

Confounding is present is each of the following situations. Explain the nature of the confounding and why the conclusions drawn may not be valid.

a) A study of proofreading compares the percent of missed errors when there is a high rate of errors (1 error in every 5 lines of text) and a low rate (1 error in every 20 lines of text). A document is prepared in which the first part has a high error rate and the second part a low error rate. Twenty people who proofread the document have any average missed error rate which is similar on both parts of of the document. It is concluded that there is not a relationship between the error rate in a document and the proofreading accuracy.

b) In a geriatric study samples of people over 65 from a general community and from a retirement community are followed. At the end of two years it is found that a larger proportion of the people continue to reside in the retirement community than in the general community. It is concluded that the retirement community living allows elderly to maintain their independence longer than does the general community living.

Answer 1