# ISS (Statistical Services) Statistics Paper III: Questions 1 - 6 of 96

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## Question number: 1

» Applied Statistics » Time Series Analysis » Economic Time Series & Components

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

List the main components of a times series. Explain the method of link relative for measurement of seasonal fluctuations of a times series.

### Explanation

The main components of a times series are the following:

(i) Secular Trend (T) : Long term movements in the mean

This measures smooth and regular long-term movements of a times series delineating the increasing, decreasing or stagnant trend over a long span of time.

(ii) Seasonal Variation (S) :

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## Question number: 2

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

Explain the principles of forming strata and clusters. What are the difference between stratified sampling and clusters sampling?

### Explanation

The principles of forming strata for a population are summarized below:

(i) The strata should be non-overlapping and should together comprise the whole population.

(ii) The stratification of population should be done in such a way that strata are homogenous within themselves.

(iii) If the limit of precision for certain

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## Question number: 3

» Applied Statistics » Index Numbers » Laspeyre

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

Discuss the considerations in the choice of (i) base period and (ii) the formula (method), for constructing price index numbers.

### Explanation

(i) Choice of base period: Price index numbers are constructed in reference to a period against which the comparisons are to be made. Such a reference period is known as base period. The index for base period is always taken to be 100. The base primarily depends upon the purpose

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## Question number: 4

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

Describe the problem of heteroscedasticity in linear regression model. Outline one method for overcoming this problem.

### Explanation

In the linear regression model, the assumption of variance of the error term is constant for all values of the independent variables does not hold, we face the problem of heteroscedasticity. This leads to unbiased but inefficient estimates that is large than minimum variance. Furthermore, the estimated variances of the

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## Question number: 5

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

Describe the two-stage least squares (2SLS) procedure for structural estimation in a simultaneous equations model. Show that it coincides with indirect least square method when the equation is exactly identified.

### Explanation

Most of the economic theory is built upon system of relationship. We will consider various estimation procedures for the system of simultaneous equation models. One of the estimation is two-stage least squares is to purify the stochastic explanatory variable Y 1 of the influence of the stochastic disturbance u. This

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## Question number: 6

Appeared in Year: 2015

Essay Question▾

### Describe in Detail

Consider a population U= {u 1, u 2, …, u n}. Observations of study variable (y) and auxiliary variable (x) are y (u i) =y i, x (u i) =x i, i = 1, 2, . . , N. Let p i =X i /X where . A sample of size n is drawn with PPSWR. Show that the population total , the estimator is an unbiased estimator. Obtain the variance of the estimator of the population total.

### Explanation

Consider a population U= {u 1, u 2, …, u n}. Observations of study variable (y) and auxiliary variable (x) are y (u i) =y i, x (u i) =x i, i = 1, 2, . . , N. Let p i =X

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