Answer:
We need a sample size of at least 650
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, 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.
In this problem:
We need a sample of size at least n
n is found when 
So
Rounding up
We need a sample size of at least 650
First, 5 students and 2 teachers is 7 different people. That means there are 7! Ways they can stand in a line. (7! Means 7x6x5x4x3x2x1)
That is 5040 ways.
Having the teachers on either side with the five students in the middle splits the question. There are 2 ways the teachers could stand (TA on left, TB on right or vice versa). There are 5! Ways to arrange the students in the middle. That is, 120. So combined, there are 2x120 ways to have them lined up with the teachers on either side. 240 ways.
Out of the 5040 ways for all of them to line up, one teacher will be in the middle 3 spaces 3/7 of the time. The second teacher will be on one of the remaining 2 central spaces 2/6 (1/3) of the time. 3/7x1/3 = 1/7. That means 1/7 or 14.29% of the time, the two teachers will occupy two of the three middle slots.
Answer:
1) 
2) 
Other conditions that are important are:
3) n is large
4) p is close to 1/2 or 0.5
Step-by-step explanation:
1) Previous concepts
The binomial distribution is a "DISCRETE probability distribution that summarizes the probability that a value will take one of two independent values under a given set of parameters. The assumptions for the binomial distribution are that there is only one outcome for each trial, each trial has the same probability of success, and each trial is mutually exclusive, or independent of each other".
2) Solution to the problem
Let X the random variable of interest, on this case we now that:
The probability mass function for the Binomial distribution is given as:
Where (nCx) means combinatory and it's given by this formula:
In order to apply the normal apprximation we need to satisfy these two conditions:
1)
2)
Other conditions that are important are:
3) n is large
4) p is close to 1/2 or 0.5
