Question

In: Statistics and Probability

Given the following discrete system, find the following x 3 4 5 6 7 P (x)...

Given the following discrete system, find the following

x 3 4 5 6 7
P (x) .4 .2 .2 .1 .1

a. E(X)

round to one decimal

b. The Variance

round to two decimals

c. Standard deviation

round to two decimals

d. find P(x ? 5)

round to one decimal using leading zeros

e. find P (x > 4)

round to one decimal using leading zeros

Solutions

Expert Solution

Solution :

From given table,

a ) E(x) = x * P(x)

= 3 * 0.4 + 4 * 0.2 + 5 * 0.2 + 6 * 0.1 + 7 * 0.1

= 1.2 + 0.8 + 1.0 + 0.6 + 0.7

= 4.3

= E(x) = 4.3

x2 * P(x) = 32 * 0.4 + 42 * 0.2 + 52 * 0.2 + 62 * 0.1 + 72 * 0.1

x2 * P(x) = 3.6 + 3.2 + 5 + 3.63 + 4.9 = 20.33

V(x) = x2 * P(x) - ()2 = 20.33 - (4.3)2 = 20.33 - 18.49 = 1.84

b ) Variance = 1.84

c ) Standard deviation = variance = 1.84 = 1.36

x2 * P(x) = 32 * 0.4 + 42 * 0.2 + 52 * 0.2 + 62 * 0.1 + 72 * 0.1

x2 * P(x) = 3.6 + 3.2 + 5 + 3.63 + 4.9 = 20.33

V(x) = x2 * P(x) - ()2 = 20.33 - (4.3)2 = 20.33 - 18.49 = 1.84

Variance = 1.84

Standard deviation = variance = 1.84 = 1.36

d ) P(x ? 5)

= P(X = 3) + P(X = 4)+ P(X = 5)

= 0.4+0.2+0.2

= 0.8

Probabilty = 0.8

e ) P (x > 4)

=  P(X = 5) + P(X = 6)+ P(X = 7)

= 0.2+ 0.1+ 0.1

= 0.4

Probabilty = 0.4


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