I thought I understood the formula, but I can't figure out how to set it up for this problem. compute.jpg
I thought I understood the formula, but I can't figure out how to set it up for this problem. compute.jpg
this formula http://sph.bu.edu/otlt/MPH-Modules/B...eanFormula.png
. . . . .[tex]\bar{x} \, =\, \dfrac{\Sigma X}{n}[/tex]
Last edited by stapel; 09-12-2013 at 11:41 AM. Reason: Providing formula inside post.
I am pretty sure I plugged the stuff in wrong. here's what I did for Set A
E20/6 = 5x10
E3.3 = 50
E=15.1
and set B
E20/6 = 50x10
E3.3=500
E=151.5
Okay that is not the way to work with mean (or average).
Tell us the definition of mean (or average).
“... mathematics is only the art of saying the same thing in different words” - B. Russell
mean is when you add all the numbers up and divide by how many there are
10+20/6 = Set A is 5?
and 500+20/6= Set B is 86.7 ? are those right? I did that without the formula because the formula confuses me.
The formula is not confusing. The problem is confusingly worded because it changes the definitions of the sets.
For set [tex]A = \{x_1,\ x_2,\ x_3,\ x_4,\ x_5\}.[/tex]
[tex]\displaystyle \bar x_A = \dfrac{\displaystyle \sum_{i=1}^5x_i}{5} = 10 \implies\sum_{i=1}^5x_i = 5 * 10 = 50.[/tex] Follow that?
Now let's define a new set [tex]H = \{x_1,\ x_2,\ x_3,\ x_4,\ x_5\, x_6\},\ where\ x_6 = 20.[/tex]
So [tex]\displaystyle \bar x_H = \dfrac{\displaystyle \sum_{i=1}^6x_i}{6}.[/tex] Still using the formula.
But what is the numerator in that formula equal to?
Here is the trick
[tex]\displaystyle \sum_{i=1}^6x_i = \left(\sum_{i=1}^5x_i\right) + x_6.[/tex] Does that make sense?
And we know what the two terms on the right of the equation equal.
[tex]\displaystyle \sum_{i=1}^6x_i = 50 + 20 = 70 \implies \bar x_H = \dfrac{70}{6} \approx 11.67[/tex]
Now try the second problem on your own, and let us know what you get.
50x10= 500
500+20= 520
520/6 = 86.7
still wrong? lol
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