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.

Graphical calculation for mode, For calculating the mode of the grouped dat...

For calculating the mode of the grouped data graphically, the following procedure is adopted. Draw a histogram of the data; the modal class is the tallest rectangle.

Muti linear regression model problem, Muti linear regression model problem ...

Muti linear regression model problem An investigator is studying the relationship between weight (in pounds) and height (in inches) using data from a sample of 126 high school

Mean deviation, First Moment of Dispersion or Mean Deviation Mean devia...

First Moment of Dispersion or Mean Deviation Mean deviation or the average deviation is the measure if dispersion which   is based upon all the items in a variable .It is the a

Two methods of isolating trend values in a time series, a) What is meant by...

a) What is meant by secular trend? Discuss any two methods of isolating trend values in a time series.

Histogram, Histogram: It is generally used for charting continuous fre...

Histogram: It is generally used for charting continuous frequency   distribution. In histogram, data are plotted as a series  of rectangle one over the other. Class intervals

Agreement, Agreement The degree to which different observers, raters or ...

Agreement The degree to which different observers, raters or diagnostic the tests agree on the binary classification. Measures of agreement like that of the kappa coefficient qu

Coefficient of variation, Coefficient of Variation The standard dev...

Coefficient of Variation The standard deviation discussed above is an absolute measure of dispersion. The corresponding relative measure is known as the coefficient of vari

Good average, Examine properties of good average with reference to AM, GM, ...

Examine properties of good average with reference to AM, GM, HM, MEAN MEDIAN MODE

Trying to find test statistic and P value, Ask question #Minimum The data i...

Ask question #Minimum The data in the accompanying table give the weights? (in g) of randomly selected quarters that were minted after 1964. The quarters are supposed to have a med

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