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Bota 302: Biostatistics Question Paper

Bota 302: Biostatistics

Course:Biostatistics

Institution: Chuka University question papers

Exam Year:2012

1
CHUKA UNIVERSITY
COLLEGE
UNIVERSITY EXAMINATIONS
BOTA 302: BIOSTATISTICS
STREAMS: TIME: 2 HOURS
DAY/DATE: TUESDAY 11/12/2012 2.30 P.M – 4.30 P.M.
INSTRUCTIONS:
Answer all questions from Section A and any two from Section B.
SECTION A: 30 MARKS
Q1. (a) State the conditions under which each of the following measurement scales are
used in research. [4 marks]
(i) Nominal scale
(ii) Ordinal scale
(iii) Interval scale
(iv) Ration scale
(b) Distinguish between [6 marks]
(i) Inferential statistics and Descriptive statistics
(ii) Sample and population
(iii) Observation and variable
Q2. (a) Using the following data, determine
(i) Mean [3 marks]
(ii) Variance [4 marks]
2
(iii) Standard deviation [2 marks]
(iv) Modal class [1 mark]
Length of fish (mm) Frequency
100 – 109 7
110 – 119 16
120 – 129 19
130 – 139 31
140 – 149 41
150 – 159 23
160 – 169 10
170 - 179 3
Q3. The following are yields of two varieties of wheat (bags per hectare)
New variety 25 21 24 20 26 23 ; n = 6.
Old variety 22 19 18 21 21 17 17 23 20 17.22 ; n = 10
(a) What statistical test would be appropriate to test the hypothesis “The yield of
the new variety is not different from that of the old variety”. [1 marks]
(b) Give the formula for that test. [2 marks]
(c) Give the number of degrees of freedom. [2 marks]
(d) What are the basic assumptions for this test? [5 marks]
SECTION B:
Q4. The use of most statistical tests such as ANOVA, t-test etc for counts is based on three
main assumptions. Discuss these assumptions as they relate to data that follow Poisson,
Positive and Negative binomial distributions. [20 marks]
Q5. (a) A simple linear relationship between two variables x and y were found to
have the estimated linear regression equation of y = 0.74 + 0.34x. If n = 16,
S
2
y.x = 0.96 and ??
2
= 184. Test for the significance of the regression
coefficient. [10 marks]
(b) Second year genetic students found that the generesponsible for an inherited
3
disease KAB, occurs in ¼ and that which causes black colour in ½ of the goat
population. The two genes segregate independently when a cross is done.
(i) What is the probability that a given individual will exhibit both traits
simultaneously? [2 marks]
(ii) What is the probability that 3 individuals picked at random will be black?
[2 marks]
(iii) What is the probability that none of the 3 would be black or have disease?
[2 marks]
(iv) What is the probability that a goat will have either the disease or black
colour? [2 marks]
(v) If 2 individuals are sampled, what is the probability that at least one of
the two will be black and has the disease? [2 marks]
Q6. Data were given for wing and tail lengths among birds of a particular species as follows:
Wing length (cm) Tail length (cm)
21.8 15.8
22.6 16.2
23.1 16.8
21.4 15.4
21.6 15.7
22.5 15.8
22.0 15.5
22.7 16.5
23.4 16.4
22.3 16.7
23.8 17.6
21.4 15.2
Calculate ??, ??, ??
2
, ??
2
and ???? and test whether there is correlation between the
wing and tail length. [20 marks]
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Bota 302: Biostatistics Question Paper

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