In Example 41 t, we showed that the covariance of the multinomial random variables N i and N j is equal to − m P i P j , by expressing N i and N j as the sum of indicator variables. We could also have obtained that result by using the formula var ( N i + N j ) = var ( N i ) + var ( N j ) + 2 cov ( N i , N j ) a. What is the distribution of N i + N j ?. b. Use the preceding identity to show that cov ( N i , N j ) = − m P i P j
In Example 41 t, we showed that the covariance of the multinomial random variables N i and N j is equal to − m P i P j , by expressing N i and N j as the sum of indicator variables. We could also have obtained that result by using the formula var ( N i + N j ) = var ( N i ) + var ( N j ) + 2 cov ( N i , N j ) a. What is the distribution of N i + N j ?. b. Use the preceding identity to show that cov ( N i , N j ) = − m P i P j
Solution Summary: The author explains that the sum of multinomial random variables has a binomial distribution. For obtaining the result, we could have used Var(N_i
In Example 41 t, we showed that the covariance of the multinomial random variables
N
i
and
N
j
is equal to
−
m
P
i
P
j
, by expressing
N
i
and
N
j
as the sum of indicator variables. We could also have obtained that result by using the formula
var
(
N
i
+
N
j
)
=
var
(
N
i
)
+
var
(
N
j
)
+
2
cov
(
N
i
,
N
j
)
a. What is the distribution of
N
i
+
N
j
?.
b. Use the preceding identity to show that
cov
(
N
i
,
N
j
)
=
−
m
P
i
P
j
Definition Definition Measure of how two random variables change together. Covariance indicates the joint variability or the directional relationship between two variables. When two variables change in the same direction (i.e., if they either increase or decrease together), they have a positive covariance. When the change is in opposite directions (i.e., if one increases and the other decreases), the two variables have a a negative covariance.
Among a student group 54% use Google Chrome, 20% Internet Explorer, 10% Firefox, 5% Mozilla, and the rest use Safari. What is the probability that you need to pick 7 students to find 2 students using Google Chrome? Report answer to 3 decimals.
Samples of rejuvenated mitochondria are mutated (defective) with a probability 0.13. Find the probability that at most one sample is mutated in 10 samples. Report answer to 3 decimal places.
The same final exam of the astronomy course was given to two groups of students. The maximum number of points that a student can score is 100. The first group consisted of a random sample of 10 students who were taught by Professor A. Students from the first group obtained the following results:
87 88 91 88 86 92 81 93 73 99
The second group consisted of a random sample of 9 students who were taught by Professor B. Students from the second group obtained the following results:
74 74 79 97 67 88 86 83 78
Compute the mean squares of between-group variability, MSBET. Round your answer to two decimal places.
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