Standard deviation for grouped data, Applied Statistics

Assignment Help:

Grouped data 

For grouped data, the formula applied is  σ = 1926_standard dviation for grouped data.png

Where f = frequency of the variable, μ= population mean.

Example 17

 

A security analyst studied hundred companies and obtained the following Return on Investment (ROI) data for the year 20x3.

Returns %

0-10

10-20

20-30

30-40

No. of companies

19

32

41

8

We can find how the ROI of the company varies with the mean ROI by calculating the standard deviations for the above data.

The steps involved are:

  • Find mean for grouped data.

  • Find deviations from mean for grouped data.

  • Find squares of the above deviations.

  • Total the squared deviations taking frequency into account.

  •  Calculate square root.

Return on investment

Mid-point

No. of companies

Deviation

%

X

f

fX

   X - μ

 f(X -  μ  )2

0-10

5

19

95

      -13.8

3618.36

10-20

15

32

480

-3.8

462.08

20-30

25

41

1025

6.2

1576.04

30-40

35

8

280

16.2

2099.52

Total

 

100

1880

 

7756.00

Mean

2299_standard dviation for grouped data1.png

= 18.8%.
 

 


Standard Deviation 

=

775_standard dviation for grouped data2.png
  = 309_standard dviation for grouped data3.png =8.81%

Thus, the standard deviation for the return on investment is 8.8%.

In such a calculation, we always assume that all the observations in a class interval are located at the mid-point of the class. For example, the first class interval has mid-point 5 and frequency 19. Hence the assumption is that all the 19 companies have an ROI of exactly 5%.


Related Discussions:- Standard deviation for grouped data

What are the charateristics of a population for which, what are characteris...

what are characteristics of a population for which it would be appropiate to use mean/median/mode

Accelerated failure time model, Accelerated Failure Time Model A basic m...

Accelerated Failure Time Model A basic model for the data comprising of survival times, in which the explanatory variables measured on an individual are supposed to act multipli

Calculate the line of best fit, The manager of Pizza Hut provides a deliver...

The manager of Pizza Hut provides a delivery service for customers who telephone in an order. The manager would like to give callers an idea of the time it will take to deliver an

Uses of arithmetic mean, Uses Arithmetic mean is widely used beca...

Uses Arithmetic mean is widely used because of the following reasons: Mean is the simplest average to understand and easy to compute. It

Team Collaboration: Business Decision Making Project, Collect data about th...

Collect data about the chosen business problem or opportunity at the company. Explain how you obtained a suitable sample of either qualitative or quantitative data. Review data f

Sampling, Sampling A  Population  is a collection of all the data point...

Sampling A  Population  is a collection of all the data points being studied. For example, if we are studying the annual incomes of all the people in India, then the population

Data project, Choose any published database from the internet or Bethel lib...

Choose any published database from the internet or Bethel library (such as those from the Census Bureau or any financial sites). You may opt to use one of the data files provided b

Correlation, Correlation The correlation is commonly used and a useful...

Correlation The correlation is commonly used and a useful statistic used to describe the degree of the relationships between two or more variables. Pearson's correlation refle

Angle count method, Angle Count method The method for estimating the pr...

Angle Count method The method for estimating the proportion of the area of a forest which is in fact covered by the bases of trees. An observer goes to each of the number of po

Chi square test for more than two rows, Using Chi Square Test when more tha...

Using Chi Square Test when more than two Rows are Present   To understand this, let us consider the contingency table shown below. It gives us the information about the stage

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd