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Szl 303: Biostatistics (Cat Ii) Question Paper
Szl 303: Biostatistics (Cat Ii)
Course:Microbiology And Biotechnology
Institution: University Of Nairobi question papers
Exam Year:2014
UNIVERSITY OF NAIROBI
School of Biological Sciences
SZL 303: BIOSTATISTICS (CAT II)
3rd Dec 2014
Instructions: Answer ALL questions (Total Marks 30)
1. Suppose that 28 cancer deaths are among workers exposed to asbestos in a building materials plant from 1981 to 1985. Only 20. 5 cancer deaths are expected from statewide mortality rates. Suppose that we want to know if there is a significant excess of cancer deaths among these workers. Is a one or two sided test appropriate here? (1 mark)
2. Assume that the test scores for a large class are normally distributed with a mean of 74 and a standard deviation of 10. Suppose that the teacher wants to limit the number of A grades in the class to no more than 20%. What would be the lowest score for an A? (3 marks)
3. A population of one year- old children’s chest circumferences has a mean of 47.0 cm and a variance of 144 cm. What is the probability of drawing from it a random sample of nine measurements that has a mean larger 50.0 cm? (3 marks)
4. A hospital ward has 10 beds. If on a particular day, the hospital admits 15 people in this ward, in how many ways can the matron assign the patients in order? (3 marks)
5. In clinical trials, a certain drug has an 8% success rate of curing a known disease. If 15 people are known to have the disease, what is the probability of at most 2 being cured? (3 marks)
6. The following data are weight change of humans tabulated after administration of a drug proposed to result in weight loss; 0.2, -0.5, -1.3, -0.7, 0.4, -0.1, 0.0, -0.6, -1.1, 0.0, -0.6, -1.1,-1.2 and -0.8. Each weight change (in Kg) is the weight after minus the weight before drug administration. Test the hypothesis that the drug does not cause a weight change. (3 marks)
7. Each of 126 individuals of a certain mammal species was placed in an enclosure containing equal amounts of each of six different foods. The frequency with the animals chose each of the foods was:
Food item (i) Frequency
1 13
2 26
3 31
4 14
5 28
6 14
Test the hypothesis that there is no preference among the food items.
8. Assuming that the variables given below are mid-points, calculate the corresponding lower and upper quantities, third decile and 20th percentile. (6 marks)
Variable 2.5 7.5 12.5 17.5 22.5
Frequency 7 18 25 30 20
9. A total of 24 seedlings of the same size were planted at the time, 12 on each of the two sides of a building. The height after several years of growth are presented in the table below:
North South
6.9 7.8
7.0 7.9
7.1 8.1
7.2 8.3
7.3 8.3
7.3 8.4
7.4 8.4
7.6 8.4
7.8 8.6
8.1 8.9
8.3 9,2
8.5 9.4
Test the hypothesis that these heights came from populations with identical medians. (5 marks)
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