Biostat 324-internal 2005

Universal Science College (B. Sc. Biochemistry) Sixth Semester 2005

Internal Examination Subject: Biostat 324 (Biostatistics) Date: July 30, 2005

Full Marks: 100 Pass Marks: 45 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates full marks. Group (A) Long Questions (Any three)

(3× ×14 = 42)

1. Explain the importance of Biostatistics in medicine, various types of biological data and clinical trials. 2. The following table shows the ages and blood pressure of 10 women: Age (X, years) 56 42 36 47 49 42 60 72 63 55 Blood Pressure (Y,mmHg)147 125 118 128 145 140 155 160 149 150 i) Find the correlation coefficient between X and Y ii) Determine the least square regression equation of Y an X. iii) Estimate the blood pressure of a woman whose age is 45 yrs. 3. a. A husband and wife appeared in an interview for two vacancies for the same post. The probability of husband's selection is 1/7 and that of wife is 1/5. What is the probability; (i) Both of them will be selected (ii) Only one of them will be selected. iii) None of them will be selected. b. The following table shows the number of days in a period of 50 days during which automobile accidents occurred in a certain part of the city. Fit a Poisson distribution for the data: No. of accidents: 0 1 2 3 4 No. of days: 19 18 8 4 1 4. The number of automobile accidents per week in a certain community were as follows: 12, 8, 20, 2, 14, 10, 15, 6, 9, 4. Are these frequencies in agreement with the belief that accident conditions were the same during the 10 week periods under considerations? Group (B) Short Questions: (Any six) (6× ×7 = 42) 1. Explain the role of statistics in preventive medicine. 2. Explain the scope of biostatistics and Epidemiology. 3. Find the mean incubation period of a disease, and coefficient of variation when 12 patients were found to have 22, 26, 30, 32, 24, 22, 28, 28, 24, 30, 28, 22 days. 4. Calculate the coefficient of correlation from the ages of husbands and wives as given below and interpret it: Husband's age(yrs): 25 30 35 40 45 50 55 Wife's age(yrs): 21 25 28 30 38 43 51 5. An unbiased coin is tossed six times. Find the probability of obtaining: (a) exactly 4 heads and (b) at least one head. 6. A telephone exchange receives on an average 4 calls per minute. Find the probability on the basis of Poisson distribution of: (a) no call at all and (b) up to 4 calls per minute. 7. A sample of 500 bottles of a certain type of medicine was tested. The mean breaking strength turned out to be 14.5. Test whether the sample is from a batch of medicine having a mean breaking strength 15.6 and standard deviation 2.2. [Z0.05= 1.96] or not.

8. Two independent samples of 8 and 7 observations respectively had the following values of the variables: Sample I: 9 11 13 11 15 9 12 14 Sample II: 10 12 10 14 9 8 10 Does the two estimates of population variance differ significantly? [F0.05(6,5) = 4.95] Group (C) Write short notes on: (Any eight)

(2× ×8 = 16)

1. Write the classification of study designs. 2. Give a brief account on the observations in medicine. 3. Blood serum cholesterol levels of 10 subjects are as follows: 240, 260, 290, 245, 255, 288, 272, 263, 277, 250mg/dL Calculate mean. 4. Calculate the Spearman's rank correlation coefficient if two examiners gave the following order of qualification to 7 applicants.: I: 2 1 5 3 4 7 6 II: 1 3 2 4 7 5 6 5. What is the probability of giving a child birth by a pregnant woman on Wednesday of a week? 6. If the probability of an individual suffering from a bad reaction by a particular injection is 0.001, determine the probability of exactly three out of 2000 individuals for the reaction. 7. Write a short note on estimation. 8. In a series of boys, the mean systolic blood pressure was 120 mmHg and SD was 10 mmHg. In the same series mean height and SD were 160 cm and 5 cm respectively. Find which character shows greater variation? 9. Write a short note on sampling. 10. Calculate standard deviation for the following data of protein content on local sorghum varieties. 9, 8, 8, 9, 8, 9, 10 mg/gm. 11. The mortality rate for a certain disease is 5 persons per 1000 population. What is the probability for just 3 deaths due to this disease in a group of 600 persons? [given e-3 = 0.05] 12. Blood serum cholesterol level of 20 patients are as under: 250, 245, 280, 260, 240, 255, 285, 270, 263, 277, 258, 288, 290, 275, 247, 253, 265, 245, 270, 240mg/dL. Find the first quartile. ***