EASTERN AFRICA STATISTICAL TRAINING CENTRE
BACHELOR OF OFFICIAL STATISTICS-YEAR 1
STATISTICAL INFERENCE (STU07104): ASSIGNMRNT 1-2020/21 ACADEMIC YEAR
Instruction:
i
Answer ALL questions
ii
Submission date- 10/03/20121
1
(a) Differentiate between the following:
(i)
Descriptive and inferential statistics
(ii)
Point and interval estimation
(b) (i) Between greater and smaller confidence levels, which one is more precise?
(ii) Between greater and smaller confidence levels, which one is more reliable?
2
(a) What sample size should be taken in order to estimate to within ±0.05 the proportion
of supporters for a political party among the whole population? It is thought that the
proportion is about 0.4 and the confidence level attached to the estimate is to be 95%.
(b) An engineer claims that the mean lifetime is between 147 and 153 hours. Whith what
level of confidence can this statement be made?
3
(a) A random sample X₁, X₂…Xₙ is picked from a normal distribution N (𝜇, 1). Show
that 𝑇 =
∑𝑛
𝑖=1 𝑋²
𝑛
is an unbiased estimator of 𝜇 2 + 1.
(b) Derive 100 (1-α) percent confidence interval for the ratio between two population
variance