Answer:
8.5x10^-5
Step-by-step explanation:
Move the decimal over between the 8 and the 5, it "hops" 5 times. Since it moved over right, make it negative
Answer:
35
Step-by-step explanation:
Answer:

Step-by-step explanation:
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The t distribution or Student’s t-distribution is a "probability distribution that is used to estimate population parameters when the sample size is small (n<30) or when the population variance is unknown".
The shape of the t distribution is determined by its degrees of freedom and when the degrees of freedom increase the t distirbution becomes a normal distribution approximately.
Data given
Confidence =0.99 or 99%
represent the significance level
n =16 represent the sample size
We don't know the population deviation 
Solution for the problem
For this case since we don't know the population deviation and our sample size is <30 we can't use the normal distribution. We neeed to use on this case the t distribution, first we need to calculate the degrees of freedom given by:

We know that
so then
and we can find on the t distribution with 15 degrees of freedom a value that accumulates 0.005 of the area on the left tail. We can use the following excel code to find it:
"=T.INV(0.005;15)" and we got
on this case since the distribution is symmetric we know that the other critical value is 
The average rate of change of the population from 2007 to 2012 is

which is to say that every five years you can expect 29 more visitors.
So if there were 607 visitors in 2010, then you could expect around 607+2*29=665 visitors in the year 2020.
Answer~35
Wørk~
2x10=20
20+15=35