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Expected value

A fire station has from zero to five calls each day. It is estimated that the probability distribution for the number of calls is given below. Determine the expected number of service calls.

Number of calls012345Probability0.100.100.200.350.100.15







So i did 0x0.1+1x0.1+2x0.2+3x0.35+4x0.1+5x0.15 which gives me 2.7

what have i done wrong?
Original post by will'o'wisp2
A fire station has from zero to five calls each day. It is estimated that the probability distribution for the number of calls is given below. Determine the expected number of service calls.

Number of calls012345Probability0.100.100.200.350.100.15


So i did 0x0.1+1x0.1+2x0.2+3x0.35+4x0.1+5x0.15 which gives me 2.7

what have i done wrong?


Can't see anything wrong, other than the fact your table of probabilities is virtually unreadable.
Original post by ghostwalker
Can't see anything wrong, other than the fact your table of probabilities is virtually unreadable.


BRILLIANT LET ME FIX THAT FOR YOU

Number of calls 0 .........1 ............2 ...........3 ...........4 .............5
Probability ........0.10 .....0.10 ......0. 20 .....0.35 .....0.10 .....0.15
(edited 6 years ago)
Original post by will'o'wisp2
BRILLIANT LET ME FIX THAT FOR YOU

Number of calls 0 .........1 ............2 ...........3 ...........4 .............5
Probability ........0.10 .....0.10 ......0. 20 .....0.35 .....0.10 .....0.15


Let me fix that for you!

Number of callsProbability00.1010.1020.2030.3540.1050.15\begin{array}{|c|c|} \text{Number of calls} & \text{Probability} \\ \hline 0 & 0.10 \\ 1 & 0.10 \\ 2 & 0.20 \\ 3 & 0.35 \\ 4 & 0.10 \\ 5 & 0.15 \\ \hline \end{array}

Motto: Learn LaTeX.
Original post by ghostwalker
Let me fix that for you!

Number of callsProbability00.1010.1020.2030.3540.1050.15\begin{array}{|c|c|} \text{Number of calls} & \text{Probability} \\ \hline 0 & 0.10 \\ 1 & 0.10 \\ 2 & 0.20 \\ 3 & 0.35 \\ 4 & 0.10 \\ 5 & 0.15 \\ \hline \end{array}

Motto: Learn LaTeX.


bloody heck, nice LaTeX\LaTeX

PRSOM
Original post by ghostwalker
Let me fix that for you!

Number of callsProbability00.1010.1020.2030.3540.1050.15\begin{array}{|c|c|} \text{Number of calls} & \text{Probability} \\ \hline 0 & 0.10 \\ 1 & 0.10 \\ 2 & 0.20 \\ 3 & 0.35 \\ 4 & 0.10 \\ 5 & 0.15 \\ \hline \end{array}

Motto: Learn LaTeX.


good lord i don't know how to do tables xD

only recently learned how to make an augemnted matrix D:
the expected value is 2.7 as you say.
Original post by the bear
the expected value is 2.7 as you say.


good ol trusty bear
Original post by will'o'wisp2



what have i done wrong?


Why do you think this is wrong?
Original post by Muttley79
Why do you think this is wrong?


my lack of brain cells
Original post by will'o'wisp2
my lack of brain cells


OK - nothing serious then ...

Did you confuse it with probability and 'expect' an answer less than 1?

E(X) = mean value
Original post by Muttley79
OK - nothing serious then ...

Did you confuse it with probability and 'expect' an answer less than 1?

E(X) = mean value


is ex the mean value? so there's no difference between the expected value and mean value?

it's just that i got 2.8 the first time i put it in the calculator >.>
Original post by will'o'wisp2
is ex the mean value? so there's no difference between the expected value and mean value?

it's just that i got 2.8 the first time i put it in the calculator >.>


Think about how you find the mean from a frequency table - for E(X) you do the same but total frequency = 1 because it's the total probability.
Original post by Muttley79
Think about how you find the mean from a frequency table - for E(X) you do the same but total frequency = 1 because it's the total probability.


you add all the values divide by the number of entries

for expected you multiply the entry by the probability and all those all up...
Original post by will'o'wisp2
you add all the values divide by the number of entries

for expected you multiply the entry by the probability and all those all up...


Which is the same thing ... E(X) = mean value
Original post by Muttley79
Which is the same thing ... E(X) = mean value


i see ye

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