Maths




Bachelor of Science in Computing in Applications & Support  Semester 3 Bachelor of Science in Computing in Networking & Support  Semester 3 Bachelor of Science in Computing in Software Development  Semester 3 

Data Analysis for Computing

Christmas 2010










Dr. Fiona Lawless






Answer any FOUR questions
All questions carry equal marks



DO NOT TURN THIS PAGE UNTIL INSTRUCTED
Question 1.
(a) The following 20 numbers relate to response times recorded when the new Carrolls network was being tested:
30.9 41.1 1.2 30.6 35.2 25.8 15.0 35.8 32.9 20.7 29.7 12.4 32.7 33.5 21.6 38.9 33.2 17.9 43.6 41.2
Using a class width of 10, construct a grouped frequency distribution for this data set and then estimate the mean response time. Explain why your answer is only an estimate of the mean of this data set. (5 marks)
(b) The numbers of SPAM EMAILS received by 750 DKIT computing students over a one week period, were recorded as follows:
No of SPAM EMAILS Received Number of students 
less than 5 68
between 5 and 10 176
between 10 and 15 244
between 15 and 20 193
between 20 and 25 42
between 25 and 30 27
(i) Calculate the mean number of SPAM emails received by a computing student. (4 marks)
(ii) Construct a histogram for the data.
Use it to estimate the modal number of SPAM emails received. (3 marks)
(iii) Construct an Ogive for the given data set.
(3 marks)
(iv) Use your Ogive to estimate:
the median number of SPAM emails received; the interquartile range; the proportion of students who receivied 21 SPAM emails or more. (4 marks)
(v) Calculate the variance and standard deviation for the data. (6 marks)
(Total: 25 marks)
Question 2.
(a) The breakdown of applicants (by location & qualifications) for a post advertised by a Dundalk based computer company were as follows: Number of applicants Dundalk Dublin  Elsewhere
Nongraduate 57 20 15
Graduate  99 69 40
If one of the applicants is selected at random, find the probability that he/she:
(i) is from Dublin
(ii) is a graduate from Dundalk
(iii) is either from Dundalk or Dublin
(iv) is a nongraduate or is from Dublin
If the applicant selected at random is from Dundalk. What is the probability that he/ she (vi) is a graduate?
(vii) is a graduate from Tralee?
(10 marks)
(b)
A game involves throwing a die:
E1: The face is 4,
E2: The face is even.
(i) Are these two events mutually exclusive?
(ii) Are these two events independent?
(5 marks)
(c) A computer lab contains 25 computers 3 of which are faulty. If two students enter this lab together and each selects a computer to work at, calculate the probability that (i) BOTH computers are defective;
(ii) NEITHER computer is defective;
(iii) EXACTLY ONE of the two computers is defective;
(iv) AT LEAST ONE of the two computers is defective.
(10 marks)
(Total: 25 marks)
Question 3.
(a) A soccer team has only two players who will take penalties. Player A takes 83% of all penalties and scores 75% of these. Player B takes the remainder and misses 39% of the penalties he takes.
If a penalty kick is taken, find the probability that: (i) the penalty is taken by player B;...
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