Greg has $400 in his savings account. Each month he spends $50 on shoes. After how many
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Answer:
We need a sample size of at least 75.
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 .
So it is z with a pvalue of , so
Now, we 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 standard deviation is the square root of the variance. So:
With a .95 probability, the sample size that needs to be taken if the desired margin of error is 5 or less is
We need a sample size of at least n, in which n is found when M = 5. So
We need a sample size of at least 75.
Solution:
Given: zj = 3- j2, zz = - 4 + j3
Part a:
zj = 3- j2 =
zz = - 4 + j3 =
Part b:
|zj| = |3− j2| = √3² +(−2)² = √13 = 3.60
|z1| = √(3− j2)(3+ j2) = √ 13 = 3.60.
Part c:
With the help of part a:
z1z2 =