9.2 Practice Problems

1)

Iron-deficiency anemia is an important nutritional health problem in the United States. A dietary assessment was performed on 51 boys 9 - 11 years old whose families were below the poverty level. The mean daily iron intake among these boys was found to be 12.50 mg with a standard deviation of 4.25mg. Construct a 95% Confidence Interval for the true mean daily iron intake of the low SES boys?

2)

We would like to test the hypothesis that mothers with low socioeconomic status (SES) deliver babies whose birth weights are lower than “normal”. To test this hypothesis, a list is obtained of birth weights from 100 consecutive, full term, live born deliveries from the maternity ward of a hospital in a low-SES area. The mean birthweight is found to be 115 oz with a sample standard deviation of 24 oz. Suppose we know from nationwide surveys based on millions of deliveries that the mean birthweight in the United States is 120 oz. Can we actually say the underlying mean birthweight from this hospital is different than the national average? Construct a 90% Confidence Interval.

3)

A topic of recent clinical interest is the possibility of using drugs to reduce infarct size in patients who have had a myocardial infarction within the past 24 hours. Suppose we know that in untreated patients the mean infarct size is 25 (ck-g-EQ/m^2). Furthermore, in 8 patients treated with a drug the mean infarct size is 16 (ck-g-EQ/m^2) with a standard deviation of 10 (ck-g-EQ/m^2). Is the drug effective in reducing infarct size? Construct a 95% Confidence Interval for the infarct size for patients treated with this drug.