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

Statistics assignment, Need statistic assignment help. Need by Monday, 26Th...

Need statistic assignment help. Need by Monday, 26Th May. Gretl has to be used compulsory.

Determine the lower and upper fences, To study the physical fitness of a sa...

To study the physical fitness of a sample of 28 people, the data below was collected representing the  number of sit-ups that a person could do in one minute.      10    12

Questionnaire, Framing of Questionnaire: Questionnaire is a schedule of...

Framing of Questionnaire: Questionnaire is a schedule of questions which is sent to the respondents for filling in by them in their own handwriting together the information rel

JET Copies Case Problem, Read the “JET Copies” Case Problem on pages 678-67...

Read the “JET Copies” Case Problem on pages 678-679 of the text. Using simulation estimate the loss of revenue due to copier breakdown for one year, as follows: 1. In Excel, use a

Example of discrete random variable, Example of discrete random variable: ...

Example of discrete random variable: 1. What is a discrete random variable? Give three examples from the field of business. 2. Of 1000 items produced in a day at XYZ Manufa

Introduction to probability, Introduction to Probability A ...

Introduction to Probability A student is considering whether she should enroll in an MBA educational program offered by a well-known college. Among othe

Age at first marrage, get a questionnaire that captured age at first marria...

get a questionnaire that captured age at first marriage

X-bar charts, First we look at these charts assuming that we know both the ...

First we look at these charts assuming that we know both the mean and the standard deviation of the process, that is  μ and  σ . These values represent the acceptable values (bench

Concepts of statistics, what are the importance, uses,optimums and applicat...

what are the importance, uses,optimums and applications of the following in agriculture field experiments; 1.standard deviation 2.standard error 3. coefficient of variation

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