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Answer:
The 80% confidence interval for the mean number of toys purchased each year is between 7.5 and 7.7 toys.
Step-by-step explanation:
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of .
That is z with a pvalue of , so Z = 1.28.
Now, find the margin of error M as such
In which is the standard deviation of the population and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 7.6 - 0.1 = 7.5
The upper end of the interval is the sample mean added to M. So it is 7.6 + 0.1 = 7.7
The 80% confidence interval for the mean number of toys purchased each year is between 7.5 and 7.7 toys.
(- 2, - 3) is a solution to the given system of equations.
Answer: Option D
<u>Step-by-step explanation:</u>
Given equation are not presented in proper format. So, let assume the given system of are as below,
2 x - y = -1
2 x -4 y = 8
Now, subtract the second equation from the first, we get
(2 x - y) -(2 x - 4 y) = -1 -8
3 y = -9
y = -3 (obtained this when divide by 3)
Substituting y = - 3 into the first equation, we get
2 x - (-3) = - 1
2 x = - 1 + 3
x = - 2 (obtained when divide by 2)
Now, the answer is (x, y) = (- 2, - 3)
