A summary of 24 observations of x gave the following information:

∑(x-a)=-73.2 and ∑(x-a)2=2115

The mean of these values of x is 8.95.

(i) Find the value of the constant a.

(ii) Find the standard deviation of these values of x.

HELP PLZ!

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- Mar 28th 2008, 05:46 AMJay JayHelp with mean and standard deviation question.
A summary of 24 observations of x gave the following information:

∑(x-a)=-73.2 and ∑(x-a)2=2115

The mean of these values of x is 8.95.

(i) Find the value of the constant a.

(ii) Find the standard deviation of these values of x.

HELP PLZ! - Mar 28th 2008, 09:41 AMmathceleb
Since no probability is given, we denote the mean of x as

We know n is 24, and . Therefore,

Your problem gives

That can be rewritten as .

<------ from above

I'll take a stab at part (ii) as well.

From above, for your second equation, substitute our value of 288 for a, we get

Expanding and simplifying, we get:

<------ remember that from part i

Now, we know that Variance, denoted as

Plugging in our value for and simplifying, we get:

<---- we figured out earlier and

Now calculate standard deviation, denoted as

- Nov 18th 2009, 10:53 PMBabyMilo
um... which one is right?

http://www.mathhelpforum.com/math-he...tml#post407749