A standard screening test for a specific genetic condition is based on a combination of maternal age and the

1. A standard screening test for a specific genetic condition is based on a combination of maternal age and the level of serum A.  Using this test 80% of these cases can be identified at birth, while 5% of normals are detected as positive.

a. What is the sensitivity and specificity of the test?

b. Assume that 1/500 births have this genetic condition.  What is the percentage of births who test positive using this test will actually have the condition?

2. To test the primary hypothesis of a study, infants were categorized by gestational age and were designated as having a severe disease if they had a concentration of a certain hormone which was 2.6 sd below the mean score for the assay from their specimen. Assume also that these assays are done in batches of 240 specimens and that a mean and sd were calculated for each batch based on a sample size of 240.  Children in the study were given a standard mental development test at <30 months of age.  The results are shown in the table below:

a. Perform a test to compare the mean score of the developmental test between children with and without the severe disease (report a p-value).

b. Suppose that we wanted to use data on children of all gestational ages in the study.  Suggest a type of analysis that could be used to relate the score on the developmental test to severe disease while controlling for age. (just suggest an analysis don’t actually do it)

3. The following table represents blood pressure recordings on one participant for 10 consecutive days with two readings per day:

a. Estimate the between-day and within-day components of variance for this participant.

b. Is there a difference in underlying mean blood pressure by day for this participant?

4. Suppose that we had a study that looked at the risk of cavities in 3 different communities according to whether their drinking water had “higher” fluoride concentration as determined by water samples.  The table below shows the data (collected over 5 years) on the number of cavities between the higher fluoride vs control for people ages 20-35 and 55-80.

What test can be used to compare the cavity rates in these two communities while controlling for age?

b.Implement the test and report a p-value.

c.Estimate the OR relating higher fluoride and cavities while controlling for age.

d.Provide a 95% confidence interval for the OR in part (c).