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

Find out the probability, There are n seats on an airplane and n passengers...

There are n seats on an airplane and n passengers have bought tickets. Unfortunately, the first passenger to enter the plane has lost his ticket and, so he just chooses a seat at r

Statistical inquiry, Main stages of Statistical Inquiry The following a...

Main stages of Statistical Inquiry The following are the various stages of a statistical inquiry (1)   Planning the Inquiry: First of all we have to assess the problem und

Aviation legislation - SUPPLEMENTAL TYPE CERTIFICATION, JAR 21 SUPPLEMENTAL...

JAR 21 SUPPLEMENTAL TYPE CERTIFICATION JAR 21 Part E introduces the need for Supplemental Type Certification when a manufacturer wishes to make major changes to the Type Desig

Find a nash equilibrium, 2 bidders have identical valuations of an object f...

2 bidders have identical valuations of an object for sale. The value of the object is either 0; 50 or 100, with equal probabilities. The object is allocated to one of the bidders i

Evaluate gross reproduction rate, Evaluate Gross Reproduction Rate: Fr...

Evaluate Gross Reproduction Rate: From the data given below compute : i)   General  Fertility  Rate ii)  Specific  Fertility  Rate iii)  Total  Fertility  Rate iv)

Weighted arithmetic mean, Weighted Arithmetic Mean Another aspect...

Weighted Arithmetic Mean Another aspect to be considered is the importance we assign to each observation. The arithmetic mean as we calculated it so far gives equal

Probability, Ask queFrom these studies, which of the following may be consi...

Ask queFrom these studies, which of the following may be considered a variable that can have a probability distribution? [I] Percentage of Sub-Saharan Africans that smoke [II] Perc

Option price binomial tree, Modify your formulas from (1) to compute the pr...

Modify your formulas from (1) to compute the price at time 0 of an American put option with the same contract speci cations in the binomial model. Report the price of the American

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