Gujarat Technological UniversityWinter 2023 Examination

GTU 3130006 Probability and Statistics (PS) Winter 2023 Paper Solution & PDF

B.E. · Computer Engineering · Semester 3 · Subject Code: 3130006
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Total Marks70 MarksExternal theory exam
Passing Marks23 Marks33% minimum cutoff
Exam Duration2.5 Hours10:30 AM – 1:00 PM
Paper Structure5 QuestionsWith internal OR choices
Jump toQ1Q2Q3Q4Q5

Question 1

14 MarksMedium
(a)
Define and give examples of Random Experiment and Sample space.
3 Marks
(b)

For a certain model car, the probability of the air conditioner failing before the warranty expires is 0.36, the probability of alternator failing is 0.26, and the probability of both failing is 0.11. Find the probability of the air conditioner or the alternator failing before the warranty expires.

4 Marks
(c)

A microchip company has three machines that produce the chips. Machine- I produces 45% of the chips, but 5% of its chips are defective. Machine-II produces 35% of the chips and 10% of its chips are defective. Machine-III produces the rest of the chips and 2% of its chips are defective. Find the probability of: A randomly selected chip is found to be

ia defective chip that has come from Machine-I,
iia non-defective chip that has come from Machine-II,
iiia defective chip that has come from Machine-III.
7 Marks

Question 2

14 MarksMedium
(a)
Define Exponential Distribution and Gamma distribution.
3 Marks
(b)

The following table gives the number of aircraft accidents that occurred during the various days of the week. Find whether the accidents are uniformly distributed over the week. (Use 𝜒2 at 5% level of significance for 6 degree of freedom is 12.59). Days Sun. Mon. Tue. Wed. Thu. Fri. Sat. No. of Accidents 14 16 8 12 11 9

4 Marks
(c)
Fit a second-degree parabola for the following data:

x: 0 1 2 3 4 y: 3 6 11 18 27 Estimate the value of y when x = 5.

7 Marks
OR OPTION
(c)
Fit a relation of the form 𝑦 = 𝑎𝑏𝑥 for the following data by the method of least squares:

x: 2 3 4 5 6 y: 8.3 15.4 33.1 65.2 126.4 Estimate the value of y when x = 1.

7 Marks

Question 3

14 MarksMedium
(a)

An insurance company has discovered that only 0.1% of the population is involved in a certain type of accident every year. If its 1000 policy-holders are selected at random from the population, what is the probability that not more than 2 of its clients are involved in such accident next year?

3 Marks
(b)

Suppose that the current measurements in a strip of wire are assumed to follow a normal distribution with a mean of 10 milliamperes and variance of 4 (milliamperes)2. What is the probability that a measurement (i) exceeds 13 milliamperes, (ii) is at most 10 milliamperes, (iii) between 10 and 13 milliamperes? [ Use: P(Z ≤ 1.5) = 0.9332].

4 Marks
(c)

Each sample of water has a 10% chance of containing a particular organic pollutant. Assume that the samples are independent with regard to the presence of the pollutant. Find the probability that in next 10 samples, (i) exactly 2, (ii) at least 4, (iii) between 2 and 7, samples contain the pollutant.

7 Marks
OR OPTION
(a)

Form the binomial distribution for the experiment of tossing a coin three times and counting the number of heads appear.

3 Marks
(b)

In a normal distribution 31% of items are under 45 and 8% are over 64. Find the mean and standard deviation of the distribution. [Use: P(0 < Z < 1.405) = 0.42, and P(0 < Z < 0.495) = 0.19].

4 Marks
(c)

For the case of the thin copper wire, suppose that the number of flaws follows a Poisson distribution with mean of 2.3 flaws per millimeter. Determine the probability of

iexactly 2 flaws in 1 millimeter of wire, (ii) at least 1 flaw in 2 millimeters of wire,
iiibetween 2 and 5 flaws in 1 millimeter of wire.
7 Marks

Question 4

14 MarksMedium
(a)

For the following data, which of the series A and B shows greater variation? Series Mean Standard Deviation A 160 10 B 60

3 Marks
(b)

In a partially, destroyed record on analysis of correlation data, only the following are legible: Variance of x, 𝜎𝑥 2 = 9, regression equation 8x – 10y + 66 = 0, 40x – 18y = 214. Find (i) mean values of x and y, (ii) the standard deviation of y.

4 Marks
(c)
Ten competitors in a contest are ranked by three judges in the following order:

1st Judge 1 6 5 10 3 2 4 9 7 8 2nd Judge 3 5 8 4 7 10 2 1 6 9 3rd Judge 6 4 9 8 1 2 3 10 5 7 Use the correlation coefficient to determine which pair of judges has the nearest approach.

7 Marks
OR OPTION
(a)
Calculate Pearson’s coefficient of skewness for the following data:

x: 12 17 22 27 32 f: 28 42 54 108 129

3 Marks
(b)

The number of messages sent per hour over a computer network has the following probability distribution: X = No. of messages 10 11 12 13 14 15 P(x) 0.08 0.15 0.30 0.20 0.20 0.07 Determine the mean and standard deviation of the number of messages sent per hour.

4 Marks
(c)
Calculate the coefficient of correlation between x and y for the following data:

x: 65 66 67 67 68 69 70 72 y: 67 68 65 68 72 72 69 71

7 Marks

Question 5

14 MarksMedium
(a)
Define Statistical Hypothesis and types of errors occurring while testing of hypothesis.
3 Marks
(b)

To test whether a particular training improved the performance, a similar training was given to 8 participants, their scores both before and after the training are given below: Score (Before): 44 40 61 52 32 44 70 41 Score (After): 53 38 69 57 46 39 73 48 Test at 5% level of significance if the training was effective in terms of performance on the test. [Use t7,0.05 = 2.37].

4 Marks
(c)

A manufacturer of sprinkler systems used for fire protection in office buildings claims that the true average system-activation temperature is 130℉. A sample of size 𝑛 = 9 systems, when tested, yields a sample average activation temperature of 131.08℉. If the distribution of activation times is normal with standard deviation 1.5℉, does the data contradict the manufacturer’s claim at 1% level of significance. [Use Z0.01 = 2.58.]

7 Marks
OR OPTION
(a)

A random sample of size 20 from a normal population has mean 40 and standard deviation of 4. Test the hypothesis that the population mean is 45. [Use 𝑡0.05,19 = 2.09. ]

3 Marks
(b)

Analysis of a random sample consisting of size m = 20 specimens of cold-rolled steel to determine yield strengths resulted in a sample average strength of 𝑥̅ =29.8 ksi. A second random sample of size n = 25 two-sided galvanized steel specimens gave a sample average strength of 𝑦̅ =34.7 ksi. Assuming that the two yield-strength distributions are normal with 𝜎1 = 4.0 and 𝜎2 = 5.0, does the data indicate that the corresponding true average yield strengths 𝜇1 and 𝜇2 are different? Use 5% level of significance. [Use 𝑍0.05 = 1.96.]

4 Marks
(c)

Oxide layers on semiconductor wafers are etched in a mixture of gases to achieve the proper thickness. The variability in the thickness of these oxide layers is a critical characteristic of the wafer, and low variability is desirable for subsequent processing steps. Two different mixtures of gases are being studied to determine whether one is superior in reducing the variability of the oxide thickness. Twenty wafers are etched in each gas. The sample standard deviations of oxide thickness are s1 = 1.96 angstroms and s2 = 2.13 angstroms, respectively. Is there any evidence to indicate that either gas is preferable? [Use 𝐹0.05,(19,19) = 2.16. ]

7 Marks
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About this Examination Paper & Attribution

Official Gujarat Technological University (GTU) examination paper and step-by-step solutions for Probability and Statistics (PS) (Winter 2023, B.E. · Computer Engineering, Sem 3). Features complete 70-mark regular & remedial examination pattern, official marking distribution across all 5 questions, and direct 1-click official PDF download.

Transcribed for student exam preparation from Gujarat Technological University official examination archives. Questions, syllabus guidelines, and curriculum marking schemes remain the intellectual property of Gujarat Technological University.

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