Answer:
a)= 2
b) 6.324
c) P= 0.1217
Step-by-step explanation:
a) The mean of the sampling distribution of X`1- X`2 denoted by ux`-x` = u1-u2 is equal to the difference between population means i.e = 2 ( given in the question)
b) The standard deviation of the sampling distribution of X`1- X`2 ( standard error of X`1- X`2) denoted by σ_X`1- X`2 is given by
σ_X`1- X`2 = √σ²/n1 +σ²/n2
Var ( X`1- X`2) = Var X`1 + Var X`2 = σ²/n1 +σ²/n2
so
σ_X`1- X`2 =√20 +20 = 6.324
if the populations are normal the sampling distribution X`1- X`2 , regardless of sample sizes , will be normal with mean u1-u2 and variance σ²/n1 +σ²/n2.
Where as Z is normally distributed with mean zero and unit variance.
If we take X`1- X`2= 0 and u1-u2= 2 and standard deviation of the sampling distribution = 6.324 then
Z= 0-2/ 6.342= -0.31625
P(-0.31625<z<0)= 0.1217
The probability would be 0.1217
Urn 1 = 4 green balls and 6 blue balls, a total of 10 balls
Urn 2 = 6 green balls and 2 blue balls, a total of 8 balls.
Probability of blue balls:
Urn 1 : P = 6/10
Urn 2 : P = 2/8
Probability that both balls are blue:
6/10 * 2/8 = 6*2 / 10*8 = 12/80 = 6/40 = 3/20
Answer is B. 3/20
10 x 25 = 250, well 20 x 25 is just double that, its 10 doubled x 25 so he probably just added it up. repeated addition really helps with times tables.
For the first one just do the multiplication as you do normally.
For the second one, you have to put a zero behind before calculating the numbers in front
Answer:
(3x+4b)(a-2y)
Step-by-step explanation:
(3ax-6xy)+(8by-4ab)
3x(a-2y) -4b(-2y+a)
(3x+4b) (a-2y)
