Posted by **Gayle 52** on Thursday, June 6, 2013 at 7:18pm.

Consider the probability function. (Give your answers exactly.)

P(x) =

5 − x

10

, for x = 1, 2, 3, 4

(a) Find the mean.

Incorrect: Your answer is incorrect. (my answer was 1).

(b) Find the standard deviation.

(my answer was 1 also on this one. Please help, I just cant get the standard deviation.

- Math question and answer check -
**Kuai**, Thursday, June 6, 2013 at 7:28pm
You can p(x )

because x values are given

p( x ) = 5-x

p(x) = 5-1 = 4

p(x) = 5-2 = 3

p(x) = 5-3 = 2

P(x) = 5-4 = 1

What about that 10 belong to

- Math question and answer check -
**Gayle 52**, Thursday, June 6, 2013 at 7:48pm
Ok, question is this the way to work this 5-4/10, 5-3/10, 5-2/10, 5-1/10 or do you divide by 4.

- Math question and answer check -
**Kuai**, Thursday, June 6, 2013 at 7:49pm
(5-x)/10

(5-1)/10 = 0.4

(5-2)/10 = 0.3

(5-3)/10 = 0.2

(5-4)/10 = 0.1

x 1 2 3 4

P(x) 0.4 0.3 0.2 0.1

It is unclear. What is the 10 doing there

- Math question and answer check -
**Gayle 52**, Thursday, June 6, 2013 at 7:59pm
When you add up all the x's the total is 10 and it is over 10 that is how I came up with the mean of one the first time.

- Math question and answer check -
**Kuai**, Thursday, June 6, 2013 at 8:12pm
You can check question first

P(x) = (5-x)/10 or 5-x/10

it is easy to compute mean when you get p(x).

- Math question and answer check -
**Gayle 52**, Thursday, June 6, 2013 at 8:23pm
5-1/10= 4/10=.4

I do appreciate the patience that you have with me. Am I getting close to it???

- Math question and answer check -
**Kuai**, Thursday, June 6, 2013 at 8:28pm
mean = 1(.4) + 2 (.3) + 3(.2) + 4(.1)

Mean = .4 +.6 + .6 +.4

Mean = 2.0

variance = 1^2 (.4) 2^2(.3) + 3^2(.2) + 4^2(.1)

variance = .4 + 1.2 + 1.8 + 1.6

variance = 5

Standard deviation = sqrt(variance - mean^2)

Sqrt(5-2^2)) = 1

- Math question and answer check -
**Gayle 52**, Thursday, June 6, 2013 at 8:54pm
Thank you, once I see it worked out I can do others, just done one and got the mean correct so far.

- Math question and answer check -
**Kuai**, Thursday, June 6, 2013 at 10:08pm
variance = 1^2 (.4) + 2^2(.3) + 3^2(.2) + 4^2(.1

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