Probability and Statistics Questions

Higher Institute of Transport and Logistics (HITL)

Semester: First Semester

Level: 200

Year: 2015

School/Faculty: HITL

DEPARTMENT: All LECTURER(S): DR. N. Siri Konje

Academic Year: 2016/2017

COURSE CODE: TL 1106 COURSE TITLE: Probability and Statistics

DATE: 16/05/2015 HALL: PBC (1 & 3) TIME: 2 hours

Instructions: Answer all questions

THE UNIVERSITY OF BAMENDA

P.O BOX 39 Bambili

REPUBLIC OF CAMEROON

Peace-Work-Fatherland

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Question 1 (8 points)

A statistics class of 40 students took a quiz. The highest possible scores was 4 points. Ten students

score 4 points, twelve students scored 3 points, eight students 2 points, six students scored 1 point and

four students scored 0. Compute the mean, median, standard deviation, first quartile and third quartile

of the scores.

Question 2 (8 points)

a) Is the sample mean always equal to one of the values in the sample? If so, explain why. If not,

give an example.

b) Find a sample for which the median is always equal to one of the values in the sample

c) Define the following (i) an event, (ii) a random variable

d) How can random variables be distinguished

Question 3 (8 points)

a) Scores on a standardize test are approximately normally distributed with mean 480 and

standard deviation of 90.

i) What proportion of the scores is above 90

ii) What problem of the scores is between 420 and 520?

b) The sample mean and standard deviation of the filled-weight of 100 boxes are 12.05 and 0.1

respectively. Find a 95 percent and 99.7 percent interval for the mean filled weight of all the

boxes.

Question 4 (4 points)

A box contains ten laptops, 3 of which are defective. Two laptops are drawn at random and tested. Let

A be the event that the first laptop drawn is defective and let B be the event that the second laptop is

defective. Find: (i) P(A), (ii) P(A/B), (iii) P(B). Are A and B independent events? Explain

Question 5 (7 points)

Compute the correlation coefficient and the equation of the least-squares (Regression) line in of y

with respect to x of the data given in the following table. Interpret your correlation coefficient

103

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