Combined mean and standard deviation -illustration, Mathematics

Combined mean

Assume m be the combined mean

Assume x1 be the mean of first sample

Assume x2 be the mean of the second sample

Assume n1 be the size of the 1st sample

Assume n2 be the size of the 2nd sample

Assume s1 be the standard deviation of the 1st sample

Assume s2 be the standard deviation of the 2nd sample

∴ Combine mean = (n1x1 + n2x2)/(n1n2)

 

                        2267_Combined mean.png

 

 Illustration

A sample of 40 electric batteries described a mean life span of 600 hours along with a standard deviation of 20 hours.

Other sample of 50 electric batteries described a mean lifespan of 520 hours along with a standard deviation of 30 hours.

If these two samples were combined and utilized in a given project simultaneously, find out the combined new mean for the larger sample and hence find out the combined or pulled standard deviation.

                Size                    x                     s

               40(n1)              600 hours (x1)  hours (s1)

               50 (n1)             520 hours (x2)  30 hours (s2)

Combined mean = (40(600) + 50 (520))/(40 + 50)

=50,000/90

= 555.56

Combined standard deviation

 

              825_Combined mean 1.png

Posted Date: 2/18/2013 1:10:20 AM | Location : United States







Related Discussions:- Combined mean and standard deviation -illustration, Assignment Help, Ask Question on Combined mean and standard deviation -illustration, Get Answer, Expert's Help, Combined mean and standard deviation -illustration Discussions

Write discussion on Combined mean and standard deviation -illustration
Your posts are moderated
Related Questions
Find the slope of the line tangent to the graph of f(x)= 3-2ln(2x^2+4) at the point (4, F(4))

assignment on theorems on circle for class 9

Who discovered unitary method? ?

Set M= {m''s/m is a number from 5 to 10}

20 equations that equal 36

can anyone explain me the concept of quadratic equation?

For the given function recognize the intervals where the function is increasing and decreasing and the intervals where the function is concave up & concave down. Utilizes this info

Solve the linear equation: The equation relating the pressure that is denoted by P, to the force, F & the area, A, over which the force is applied is P =F/A.  Solve this equat

Marty used the subsequent mathematical statement to show he could change an expression and still get the similar answer on both sides: 10 × (6 × 5) = (10 × 6) × 5 Which mathematica

The area of a square is given by the formula width time's height. But since the square has all the sides equal, the height is of the same measure as its width. Hence its formula is