Population variance, Applied Statistics

Examining the Population Variance

Business decision making does not limit itself to setting up the hypothesis to test for the equality of more than two means or proportions simultaneously. This may be attributed to the everchanging and dynamic economic environment. It throws up situations wherein, the managers not only have to deal with the means and proportions but also have to objectively look at and probe the extent as well as the magnitude of the variability present in the population, determine the accuracy of the estimate and the degree of uncertainty that can be associated with such estimates.

In this part of the chapter, first we will look at the distribution of the sample variance for a population and conclude this chapter after looking at the distribution for the sample variance of two populations.

Inference about a Population Variance

Since it is difficult to collect information about the population in an exhaustive manner, we employ the sample variance (s2) as an estimate for the population variance (s2). The square root of s2 and s2 gives us the standard deviation of the sample and the population. But to calculate the limits, we require a sampling distribution. If the population variance s2, exhibits the characteristics of a normal distribution then the corresponding statistic is better described by a Chi Square distribution with n - 1 degrees of freedom. The Chi Square statistic for a sample variance is given by

              495_population variance.png  ......(1)

It is then possible to use Chi Square distribution to arrive at the confidence intervals for the parameter s2. Since the confidence intervals and the testing of the hypothesis is about s2 the population variance, equation (1) can be rewritten as   

951_population variance1.png

This facilitates us to find the confidence intervals for s2. The lower and the upper confidence intervals are given by

1580_population variance2.png

 

1514_population variance3.png

Figure

39_population variance4.png

Since we know the values of 1565_population variance5.png  , the square root of these two will give us the confidence interval for the standard deviation.

Posted Date: 9/15/2012 6:26:34 AM | Location : United States







Related Discussions:- Population variance, Assignment Help, Ask Question on Population variance, Get Answer, Expert's Help, Population variance Discussions

Write discussion on Population variance
Your posts are moderated
Related Questions
From the information given, what seems to be the main flaw in each of the following statistical generalisations? (i) Banking industry employees are facing a crisis, if their

Significance of Correlation The study of correlation is of immense use in practical life. Correlation analysis contributes to the understanding of economic behavior, aids in lo

The mean tax-return preparation fee H&R Block charged retail customers in 2012 was $183 (The Wall Street Journal, March 7, 2012). Use this price as the population mean and assume t

solve problems

Examples of grouped, simple and frequency distribution data

#regression line drawn as Y=C+1075x, when x was 2, and y was 239, given that y intercept was 11. calculate the residual

1. Suppose you are estimating the imports (from both the U.S. mainland and foreign countries) of fuels and petroleum products in Hawaii (the dependent variable). The values of the

Let X 1  and X 2  be two independent populations with population means μ 1  and  μ 2  respectively. Two samples are taken, one from each population, of sizes n 1  and n 2  re

Solve the following Linear Programming Problem using Simple method. Maximize Z= 3x1 + 2X2 Subject to the constraints: X1+ X2 = 4 X1 - X2 = 2 X1, X2 = 0

Differentiate between prediction, projection and forecasting.