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To find mean and standard deviation of distribution

Three tables listed below show "random variables" and their " probabilities. However, only one of these is actually a probability distribution.

A) What is it?

Table 1 Table 2 Table 3

X P(X) X P(X) X P(X)

5 .3 5 .1 5 .5
10 .3 10 .3 10 .3
15 .2 15 .2 15 -.2
20 .4 20 .4 20 .4

B) Using the correct probability distribution, find the probability that x is:

1. Exactly 15.
2. No more than 10.
3. More than 5.

C) Compute the mean, variance, and standard deviation of this distribution

Solution Preview

Table 2 is correct probability distribution.
because sum of P(x) = 1 and ...

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