LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Sc. DEGREE EXAMINATION – PLANT BIO&BIOTECH.&ADV.ZOO.
SUPPLEMENTARY EXAMINATION – APRIL 2008
ST 3203 / 3201 - BIOSTATISTICS
Date : 27-06-08
Time : 9.00 – 12.00
Dept. No.
Max. : 100 Marks
SECTION A
Answer all questions.
(10 x 2 = 20)
1. Mention any two limitations of using arithmetic mean
2. Find the 75th percentile of 31,23,17,54,66,39,40.
3. Give the difference between relative and absolute measures of dispersion.
4. What is the probability of getting a head and an even number when a coin and a die are tossed?
5. The distribution function of a random variable ‘X’ is as follows:
X:
-2
0
1
2
P[X=x]:
1/8
½
1/8
¼ Find the distribution function of
2
Y=X .
6. Give any two properties of normal distribution.
7. Define unbiased estimator.
8. The number of smokers in a random sample of size 350 from a city was found to be 125.Can it be
concluded that the proportion of smokers in the entire city is 0.5? Test at 5% level of significance.
9. Define Analysis of Variance.
10. Mention the advantage of using non parametric tests.
SECTION B
Answer any five questions.
(5 x 8 = 40)
11. Calculate mean, standard deviation and coefficient of variation of the following frequency
distribution of marks:
Marks: 0-10 10-20 20-30 30-40 40-50 50-60 60-70
No. of students: 5
12
30
45
50
37
21
12. Explain the concepts of correlation and regression with an example.
13. The incidence of occupational disease in an industry is such that the workmen have a 20% chance
of suffering from it. What is the probability that out of six men selected at random, i.) none and
ii.) exactly two and
iii.) 4 or more will contact the disease?
14. In an intelligence test administered to 1000 students, the scores of which are assumed to be
normally distributed, the average score was found to be 42 with a standard deviation of 24. Find
the number of students who got scores a.) less than 30 b.) between 38 and 60 and
c.) more than 80.
15. From a population with N=4 units having values 12, 15, 7, 10, a sample of size 2 is drawn with
replacement. Obtain the sampling distribution of range and also calculate its standard error.
16. An agency conducting a weight reduction program claims that participants in their program
achieve a weight reduction after completing 4 weeks of training. To test the agency’s claim a
random sample of 10 individuals was taken and their weight(in kgs) before and after the training
period were obtained The data obtained is as follows:
Before weight: 86 92 100 93 88 80 88 92 95 106
After weight: 77 84 92 87 80 74 80 85 95 96
Does the sample data support the agency’s claim? Test at 5% level of significance.
1
17. The yield (in pounds) obtained by three varieties of a crop are given below:
Crop A: 8 10 7 14 11
Crop B: 7
5 10
9
9
Crop C: 12 9 13 12 14.
Test at 5% level whether the average yield of the three varieties of crop are same based on the
above information.
18. Explain the procedure for testing a specified value of Population median.
SECTION C
Answer any two questions.
(2 x 20 = 40)
19 a.) Find quartile deviation and mean deviation about mean for the following data.
X: 0-10 10-20 20-30 30-40 40-50 50-60 60-70
f: 7
12
18
25
16
14
8
b.) The probability that a boy will get a scholarship is 0.9 and that a girl
will get is 0.8. What is the probability that i.) atleast one of them will get
the scholarship ? ii.) none will get the scholarship ?
(14+6)
20 a.) The following table gives the number of days in a 50 day period during
which accidents occurred in a given part of a city.
No. of accidents: 0
1
2
3
4
No. of days: 19
18
8
4
1
Fit a Poisson distribution to the above data.
b.) The following table shows the age (X) and blood pressure (Y) of 8
persons:
X: 52 63 45 36 72 85 47 25
Y: 129 145 137 124 154 147 138 120
Obtain the regression equation of Y on X and find the expected blood
pressure of a person who is 54 years of age.
(8+12)
21. a.) In a random sample of 1000 flowers from a garden, 370 were found
to be infected while in a random sample of 1200 from another garden,
435 were found to be infected. Test at 5% level whether the proportion
of flowers infected in both the gardens are same.
b.) For a random sample of 10 persons fed on diet A, the increase in
weight (in pounds) in a certain period were 10,6,16,17,13,12,8,14,15
and 9.For another random sample of 12 persons fed on diet B, the
increase in weight in the same period were 7,13,22,15,12,14,18,8,21,
23,10 and 17.Test at 5% level whether the diets A and B differ
significantly as regards their effect on increase in weight.
(8+12)
22
The following data represent the number of units of production per
day made by five workers using four different machines:
Machine
Worker
A
B
C
D
1
44
38
47
36
2
46
40
52
43
3
34
36
44
32
4
43
38
46
33
5
38
42
49
39
Test at 5% level whether the workers are equally efficient and the
machines are equally efficient.
______________________
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