Biostatistic, statistics homework help
1. Glucose levels in patients free of diabetes are assumed to follow a normal distribution with a mean of120 and a standard deviation of 16. What proportion of patients has glucose levels exceeding 115?
2. The mean total cholesterol level in women free of cardiovascular disease is 205 with a standard deviation of 19.2. What proportion of women has total serum cholesterol levels exceeding 200?
3. The gestation period for human births can be taken as normally distributed with a mean of 266 days and a standard deviation of 16 days. If a gestation period of 276 days, what percentile among human births is this?
4. Suppose that the probability of a child living in urban area in the US is obese is 20%. A social worker sees 15 children living in urban areas. What is the probability that none are obese?
5. Approximately 30% of obese patients develop diabetes. If a physician sees 10 patients who are obese, what is the probability that half of them will develop diabetes?
6. The following data was collected in survey of 8^{th} graders and summarize their cell phone status.
No of cell phone 
Conventional Cell phone user 
Smart Phone user 
Total 

Boys 
55 
65 
35 
155 
Girls 
31 
78 
27 
136 
Total 
86 
143 
62 
291 
What proportion of the 8^{th} graders has conventional cell phones?
7. BMI in children is approximately normally distributed within a mean 24.5 and standard deviation 6.2. A BMI between 25 and 30 is considered overweight. What proportion of children is overweight?
8. The following table shows a distribution of BMI in children living US and European urban neighborhoods. (The data is in millions.)
Neighborhood 
Normal weight 
Overweight 
Obese 
Total 
US 
125 
50 
40 
215 
Europe 
101 
42 
21 
164 
Total 
226 
92 
61 
379 
If a child is selected at random,
a. What is the probability they are overweight?
b. What is the probability that a child living in the US urban neighborhood is overweight?
9. The risk of hepatoma among alcoholics without cirrhosis of the liver is 24%. Suppose we observe 7 alcoholics without cirrhosis. What is the probability that exactly 1 of these 7 people have hepatoma?
10.
Screening test 
Impaired Glucose Tolerance 
Not Impaired 
Positive 
17 
13 
Negative 
8 
37 
A new noninvasive screening test is proposed that is claimed to be able to identify patients with impaired glucose tolerance based on a battery of questions related to health behaviors. The new test is given 75 patients. Based on each patient’s responses to the questions they are classified as positive, or negative for impaired glucose tolerance. Each patient also submits a blood sample and their glucose tolerance status is determined. The results are tabulated below.
a. What is the sensitivity of the screening test?
b. What is the false positive fraction of the screening test?
11. The following table shows the results of a screening test hypothesized to detect persons at risk of side effects of a cosmetic surgery.
Side Effects Positive 
Side Effects Absent 
Total 

Screen Positive 
12 
6 
18 
Screen Negative 
85 
204 
289 
Total 
97 
210 
307 
a. Compute the sensitivity of the test
b. Compute the specificity of the test
c. Compute the false positive fraction
d. Compute the false negative fraction
12. The following table shows the results of the a screening test hypothesized to identify persons at risk for rare blood disease
No Disease 
Disease 
Total 

Screen Positive 
1274 
28 
1302 
Screen Negative 
51 
45 
96 
Total 
1325 
73 
1398 
a. Compute the sensitivity of the test
b. Compute the specificity of the test
c. Compute the false positive fraction
d. Compute the false negative fraction
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