Answer:
The formula to generate 70% confidence interval is:
, in which
is the sample mean.
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:
![\alpha = \frac{1 - 0.7}{2} = 0.15](https://tex.z-dn.net/?f=%5Calpha%20%3D%20%5Cfrac%7B1%20-%200.7%7D%7B2%7D%20%3D%200.15)
Now, we have to find z in the Z-table as such z has a p-value of
.
That is z with a pvalue of
, so Z = 1.037.
Now, find the margin of error M as such
![M = z\frac{\sigma}{\sqrt{n}}](https://tex.z-dn.net/?f=M%20%3D%20z%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D)
In which
is the standard deviation of the population and n is the size of the sample.
Assume that body masses of Goldfinch birds follow a normal distribution with standard deviation equal to 0.04 oz.
This means that
.
Sample of 10 birds:
This means that
.
The margin of error is of:
![M = z\frac{\sigma}{\sqrt{n}}](https://tex.z-dn.net/?f=M%20%3D%20z%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D)
![M = 1.037\frac{0.04}{\sqrt{10}}](https://tex.z-dn.net/?f=M%20%3D%201.037%5Cfrac%7B0.04%7D%7B%5Csqrt%7B10%7D%7D)
![M = 0.013](https://tex.z-dn.net/?f=M%20%3D%200.013)
The lower end of the interval is the sample mean of
subtracted by M.
The upper end of the interval is the sample mean of
added to M.
Then, the formula to generate 70% confidence interval is:
, in which
is the sample mean.