problem1. The data set lowbwt.sav having information for a sample of 100 low birth weight infants born in two teaching hospitals in Boston. Measurements of the systolic blood pressure are saved under the variable name sbp and indications of gender—with 1 representing a male and 0 a female—under the name sex.
(a) Find a histogram of systolic blood pressure. Based on graph, do you think that blood pressure is approximately normally distributed?
(b) Employ the Shapiro-Wilks test to check for the normality of blood pressure. Carefully describe your conclusion.
(c) Find the mean and standard deviation of blood pressure by sex. prepare a short abstract of these summary statistics.
(d) Test the null hypothesis that among low birth weight infants, the mean systolic blood pressure for boys is equal to the mean for girls.
Use a two-sided test at the 5% level of significance. What do you conclude?
problem2. A number of years ago the American Academy of Pediatrics suggested that tetracycline drugs not be used for children under the age of 8. Prior to this recommendation, a two-year study conducted in Tennessee had investigated the extent to which physicians prescribed this drug in the prior two years. In the study a random sample of 770 family practice physicians were characterized according to whether the county of their practice was urban, suburban, or rural. The numbers of doctors in each of these categories who did and didn’t prescribe tetracycline to at least one child under the age of 8 are given below.
Urban County Suburban Rural
Tetracycline 65 90 172
No Tetracycline 149 136 158
Please use SPSS only for part (i) below.
(a) Identify the illustrative and the response variables in this case.
(b) For each county type, find out the percentage of physicians who prescribed tetracycline.
(c) Based on your percentages in part (b), elucidate the relationship, if any, between the two variables.
(d) find out the expected counts for the six cells under assumption that these two variables are independent.
(e) find out the value for the test statistic associated with the Chi-square test for independence.
(f) Use the Vassar applet to evaluate the p-value associated with this test.
(g) Find the odds of prescribing tetracycline for physicians in each of three county types.
(h) Find two odds ratio using urban counties as the reference. Put the odds for urban counties as the denominator in each case. Interpret your two values.
(i) You will find the raw data for this problem in the data set tetracycline.sav. Use SPSS to get your values in parts (b), (d), (e), and (f). Paste your output here.