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

Probability, 2.1 Modern hotels and certain establishments make use of an el...

2.1 Modern hotels and certain establishments make use of an electronic door lock system. To open a door an electronic card is inserted into a slot. A green light indicates that the

Break-even analysis, a. How can break-even analysis be used in selecting a ...

a. How can break-even analysis be used in selecting a new plant site? b. What are potential advantages and disadvantage of locating a production facility in foreign country i

Probability and expectation, Ten balls are put in 6 slots at random.Then ex...

Ten balls are put in 6 slots at random.Then expected total number of balls in the two extreme slots

Advantages of median, Advantages It is especially useful in c...

Advantages It is especially useful in case of open-end classes since only the position and not the values of items must be known. The median is also recommended if th

Find the conditional distribution of turning diameter, 1. Assume the random...

1. Assume the random vector (Trunk Space, Length, Turning diameter) of Japanese car is normally distributed and the unbiased estimators for its mean and variance are the truth. For

Statistics assignment, To compare three brands of computer keyboards, four ...

To compare three brands of computer keyboards, four data entry specialists were randomly selected. Each specialist used all three keyboards to enter the same kind of text material

Circul;atory ststistics Lab, What statistics can be obtained from a circula...

What statistics can be obtained from a circulatory lab?

Sampling error , Sampling Error  It is the difference between the value...

Sampling Error  It is the difference between the value of the actual population parameter and the sample statistic. Samples are used to arrive at conclusions regarding the p

Scenario- Superior Health Care System Inc., The management at Superior Heal...

The management at Superior Health Care System Incorporated recently purchased several new facilities including the central patient information management center. This purchase will

Population variance, Examining the Population Variance Business decisio...

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 sim

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