CSS 2019 Statistics Past Paper

Paper details

Examination

CSS

Year

2019

Subject

Statistics

Paper

Single Paper

Subject type

Optional

Mode

Subjective

Questions recorded from this paper

These 7 question wordings are transcribed from CSS Vista’s structured Statistics past-paper record for CSS 2019.

1. Q3 · Basic Probability(a) Define mutually exclusive events. State and prove the theorem of addition of (6) probabilities concerning mutually exclusive events. (b) Show that the multiplication law P(A Ʌ B)=P(A/B)P(B), established for two events, may be (6) generalized to three events as follows; P(A Ʌ B Ʌ C)=P(A/B Ʌ C) P(B/C) P(C) (c) There are three coins, identical in appearance, one of which is ideal and the other (8) (20) two biased with probabilities 1/3 and 2/3 respectively for a head. One coin is taken at random and tossed twice. If a head appears both the times, what is the probability that the ideal coin was chosen?
2. Q5 · Properties(a) Explain what you understand by the probability sampling and non probability (6) sampling. What are their relative advantages and disadvantages? (b) What is a sampling distribution? Describe the properties of the sampling distribution (6) of the means. (c) A finite population consists of the numbers 2, 4 and 6. Form a sampling distribution (8) (20) of sample mean, when random samples of size 4 is drawn with replacement. Also verify its properties. s2
3. Q4 · Correlation(a) (i) Explain briefly how the principle of least squares is used to find a regression (6) line based on a sample of size n. Illustrate on a rough sketch the distance whose squares are minimized, taking care to distinguish the dependent and independent variables. (ii) Find the least square estimates of parameters in a simple linear regression model Y i =α+βX i +e i where e i ’s are distributed independently with mean zero and constant variance. (iii) What are the properties of least square regression line? (b) The following means, standard deviations and correlations are found for (6) X 1 = Seed-hay crops in owts. Per acre X 2 = Spring rainfall in inches X 3 = Accumulated temperature above 42o F in spring in a certain district in England during 20 years. X�1 = 28.02, S1 = 4.42, r12 = 0.80, X�2 = 4.91, S2 = 1.10, r13 = −0.40, X�3 = 594, S3 = 85, r12 = −0.56, Find the partial correlation and the regression equation for hay-crop on spring rainfall and accumulated temperature. (c) What do you understand by nonparametric tests? Why such tests are also called (8) (20) distribution-free tests? Give the advantages and disadvantages of nonparametric tests over parametric tests. Describe the Wilcoxon signed-rank test for one sample. How does it differ from the sign test?
4. Q2 · Sampling Distribution of Mean(a) What is meant by a frequency distribution? Describe briefly the main steps in the (6) preparation of a frequency table from raw data. (b) A man travels from A to B at average speed of 30 miles per hour and returns from B (6) to A along the same route at an average speed of 60 miles per hour. Find the average speed of the entire journey. (c) Define mean-deviation and its co-efficient. Discuss its advantages and uses. (8) (20) Estimate the mean deviation from the arithmetic mean of the following set of examination marks. Marks 0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 No. of 2 3 8 24 27 40 11 5 students
5. Q6 · Proportion(a) Under what condition is the sampling distribution of s12 an F-distribution? Explain (6) the relationship between the F and t distributions, between the F and Chi-Square distributions. (b) The proportion of families buying milk from company A in a certain city is believed (6) to be p=0.6. If a random sample of 10 families shows that 3 or less buy milk from company A, we shall reject the hypothesis that p=0.6 in favour of the alternative p<0.6. Evaluate α if p=0.6, evaluate β for the alternatives p=0.3, p=0.4 and p=0.5. (c) Define a Chi-square random variable and its density function. Discuss the important (8) (20) properties of Chi-square distribution. Show that the Chi-square distribution tends to normal distribution for large degrees of freedom.
6. Q7 · Design of Experiments(a) Describe the Randomized Complete Block Design, its model and analysis. What are (6) its advantages and disadvantages? (b) Compare Randomized Complete Block experiments with Completely Randomized (6) experiments, comparing their respective advantages and relative efficiency, with illustrations. (c) Three varieties A, B and C of a crop are tested in a randomized block design with four (8) (20) replications, the layout being given below. The plot yields in pounds are also indicated therein. Analyze the experimental yields and state your conclusions. 1 A 32.1 C 34.2 B 31.7 Replications 2 C 30.7 A 17.0 B 32.7 3 A 40.8 B 25.3 C 48.2 4 B 47.9 C 59.6 A 26.8
7. Q8 · Population Analysis & Vital Statistics(a) Define gross and net production rates. Explain how would you compute the net (6) production rate and what interpretations can be made if it is 1, less than 1 or greater than 1. (b) Explain with suitable illustrations the object of standardizing various vital statistics (6) relating to births, deaths and marriages. (c) Compute the gross and net reproduction rates for the following data: (8) (20) Age-group Female Female Probability (years) Population (000) births of survival 15-19 1558 18900 0.914 20-24 1112 71100 0.899 25-29 1595 96900 0.884 30-34 1629 64200 0.868 35-39 1627 34900 0.852 40-44 1522 10800 0.834 45-49 1401 800 0.813

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