Wednesday

August 20, 2014

August 20, 2014

Posted by **ash** on Sunday, November 21, 2010 at 12:04am.

the question is;

a) compute the mean and the standard deviation of the population?

ive looked through all my notes and my textbook and i just cant figure out how to this.

thank you :)

- Math -
**MathMate**, Sunday, November 21, 2010 at 10:13amA population is a collection of data, and a sample is a subset (i.e. a smaller number of the data, obtained randomly) of the population.

The population mean, μ, is the arithmetic average of ALL the data present in the population. The sample mean is the arithmetic mean of the particular sample. It can vary from sample to sample, but is generally close to the population mean.

For example:

Consider a class of 10 children with ages 8,8,9,9,9,10,10,8,9,10.

The population mean is

μ=(8+8+9+9+9+10+10+8+9+10)/10

=90/10

=9.0

If we take a random sample, say, every second child starting from the first, we get

sample mean

=(8+9+9+10+9)

=45/5

=9.0

Which happens to be identical to the population mean. This is why often we take the sample mean to represent the population mean.

The standard deviation requires a little more calculation, it is defined, for the population, as:

σ

=√((Σ(x-μ)²)/n)

In the above case, we have

σ

=√(((8-9)²+(8-9)²+(9-9)²+(9-9)²+(9-9)²++(10-9)²+(10-9)²+(8-9)²+(9-9)²+(10-9)²)/10)

=√((1²+1²+0²+0²+0²+1²+1²+1²+0²+1²)/10)

=√(6/10)

=0.7746...

The sample standard deviation, sn is calculated similarly, with the exception that the divisor n is usually replaced by (n-1) to give a better estimate of the population standard deviation.

**Related Questions**

statistics - i have a question regarding statistics. i just don't know how to do...

Math - solve for indicated letter. f=2g, for g what is the solution for g? can ...

the remainder theorem - Please Help!! - i'm really not sure how to do this ...

Algebra I - Hi, I would like someone to explain to me the process to get to the ...

Math - Mathmate, I really appreciate all your help regarding my composite ...

MATH STUCK:-( - I am having some difficulties factoring polynomials and I use ...

science - A hydraulic jack is needed to raise an object with a force of 4000 N ...

Chemistry - A sample of C3H8 has 2.64 x 10^24 atoms. How many carbon atoms does...

Math - Hi. I found this question on a Math Counts practice test and it ...

Science/ Social Studies - I need help with those two subjects. Please tell us ...