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Old 10-05-2018, 11:07 AM
kn005 kn005 is offline
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Default calculating expected value

I have a question on how to calculate expected values when you have ranges so for eg.

probability
less than 50 27%
50- 69 14%
70- 89 15%
90 or more 47%

how do you calculate the expected value when you have ranges? do you use the midpoint for each range and multiply by the probability?

Last edited by kn005; 10-05-2018 at 11:28 AM..
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Old 10-05-2018, 11:25 AM
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And make sure your probabilities add up to 1.0. Just sayin'...
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Old 10-05-2018, 11:28 AM
kn005 kn005 is offline
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And make sure your probabilities add up to 1.0. Just sayin'...
oops i'll change it. It was just a quick example. do you use the midpoint though?
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Old 10-05-2018, 12:25 PM
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Also, how do i find the midpoint of 90 or more?
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Old 10-05-2018, 12:27 PM
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I don't think you can estimate the mean with an open ended interval unless you assume a parametric distribution, estimate parameters, and then do a chi square test to test the fit of the model.
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Old 10-05-2018, 12:42 PM
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Quote:
Originally Posted by kn005 View Post
oops i'll change it. It was just a quick example. do you use the midpoint though?
Quote:
Originally Posted by Breadmaker View Post
And make sure your probabilities add up to 1.0. Just sayin'...
.

What is the support of the underlying data? For example, are these test scores--so support on the interval [0, 100]? Or temperature (in degrees F) in Phoenix, AZ--so support on the interval [40, 110]?

It is completely reasonable to use midpoints (absent all other information) since that is the implicit assumption of uniform-distribution within a given interval.
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