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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.
Answer + Step-by-step explanation:
1) The probability of getting 2 white balls is equal to:

2) the probability of getting 2 white balls is equal to:

3) The probability of getting at least 72 white balls is:

![=\sum^{150}_{k=72} [C^{k}_{150}\times \left( \frac{8}{15} \right)^{k} \times \left( \frac{7}{15} \right)^{150-k}]](https://tex.z-dn.net/?f=%3D%5Csum%5E%7B150%7D_%7Bk%3D72%7D%20%5BC%5E%7Bk%7D_%7B150%7D%5Ctimes%20%20%5Cleft%28%20%5Cfrac%7B8%7D%7B15%7D%20%5Cright%29%5E%7Bk%7D%20%20%5Ctimes%20%5Cleft%28%20%5Cfrac%7B7%7D%7B15%7D%20%5Cright%29%5E%7B150-k%7D%5D)