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P(x) =
5 − x
10
, for x = 1, 2, 3, 4

(a) Find the mean.

(b) Find the standard deviation.

• Math question and answer check - ,

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 - ,

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 - ,

(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 - ,

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 - ,

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 - ,

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 - ,

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 - ,

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 - ,

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