CSIT 3rd Semester
Statistics II Board Question Paper 2080

STA 215-2080 ✡
Tribhuvan University
Institute of Science and Technology
2080
✡
Bachelor Level/Second Year/Third Semester/Science
Computer Science Information Technology (STA 215)
(Statistics II)
(New Course)
Full Marks:60 Pass Marks:24 Time:3 hours

Candidates are required to give their answers in their own words as for as practicable.
The figures in the margin indicate full marks

Section A
Long Answer Questions
Attempt any Two question.
[2x10=20]
1.

A computer manager needs to know how efficiency of her new computer program depends on the size of incoming data and how many tables are used to arrange each data set. Efficiency will be measured the number of processed requests per hour. Applying the program to data set of different sizes and number of tables are used, she gets the following results.

Processed requests, Y16261141505540
Data size, (gigabytes), X₁1510108776
Number of tables, X₂12101020204

The regression equation obtained is: Y=52.7 -2.87 X₁+0.85 X₂.
Total sum of square=1452
Sum of due to regression=1143.3.
a) Interpret the values of regression coefficients b₁ and b₂
b) Test the significance of the regression model at 0.05 level of significance.
c) Is there significant relationship between processed request and number of tables at 0.05 level of significance? Given, standard error of b₂=0.55.
d) What percentage of variation of processed requests is explained by data size and number of tables?
e) Compute standard error of estimate.
f) Estimate the number of processed requests if data size is 9 gigabytes and number of tables used are 8.

2.

In an experiment to determine which of three different missile systems is preferable, the propellant burning rate is measured. The data after coding are given in the table. Use Kruskal-Wallis test (significance level of 0.01) to test the hypothesis that the propellant burning rates are same for the three missile systems.

Missile system I22.316.722.719.318.5
Missile system II23.419.517.520.816.019.9
Missile system III18.419.517.818.019.622.817.1

3.

What is the Latin Square Design? Under what conditions can this design be used? Give the lay out and analysis of Latin Square Design.

Section B

Attempt any Eight questions

[8x5=40]
4.

What do you understand by estimation? If we want to determine average mechanical aptitude of a large group of workers, how large a random sample is need to be able to assert with probability 0.95 that the sample mean will not differ from the true mean by more than 2.0 points? Assume that population standard deviation is 10.

5.

Define level of significance. Describe type I and type II errors.

6.

A random sample of students is asked their opinion on proposed core curriculum change. The results are as follows:

ClassOpinion
FavoringOpposing
Freshman12080
Sophomore60140
Junior5050
Senior4053

Test the hypothesis that opinion on the change is independent of class standing. Use 0.01 significance level.

7.

Define Central limit theorem. The life of a certain brand of an electric bulb may be considered a random variable with mean 1350 hours and standard deviation 550 hours. Using central limit theorem, find the probability that the average life time of 100 bulbs exceeds 1440 hours.

8.

Define multiple correlation. In a trivariate distribution X₁, X₂ and X₃, the simple correlation coefficients are given as r₁₂= 0.5, r₂₃=0.6, r₁₃=0.7. Find
(i) partial correlation coefficient between X₁ and X₂ keeping X₃ constant.
(ii) multiple correlation coefficient assuming X₁ as dependent variable.

9.

What do you understand by Design of Experiment? Prepare one way analysis of variance table and carry out the test for the significance of difference in the average yields between three different varieties of seed. Given:
Total sum of squares = 258
Sum of square between varieties of seed = 50
Total number of observations = 20

10.

Define type I and type II error in testing of hypothesis. It is claimed that Samsung and Huawei mobiles are equally popular in Kathmandu. A random sample of 600 people from Kathmandu showed 350 have Samsung mobile. Test the claim at 5% level of significance.

11.

Customers of certain internet service provider connect to the internet at the average rate of 10 new connections per minute. Connections are modelled by binomial counting process.
a) What frame length gives the probability 0.1 of an arrival during given frame?
b) Find the mean and variance for the number of seconds between two consecutive connections.

12.

Write short notes on any two:
a) Difference between parametric and non-parametric test.
b) Required assumptions for linear regression model.
c) Stochastic process.