An observational study is retrospective if it considers only existing data. It is prospective if the study design calls for data to be collected as ti

The centers for Disease Control reported the percentage of people 18 years of age and older who smoke (CDC website, December 14, 2014). Suppose that a study designed to collect new data on smokers and Questions Navigation Menu preliminary estimate of the proportion who smoke of .26.
a) How large a sample should be taken to estimate the proportion of smokers in the population with a margin of error of .02?(to the nearest whole number) Use 95% confidence.
b) Assume that the study uses your sample size recommendation in part (a) and finds 520 smokers. What is the point estimate of the proportion of smokers in the population (to 4 decimals)?
c) What is the 95% confidence interval for the proportion of smokers in the population?(to 4 decimals)?

1. Which of the following statements is incorrect?
The median is the most appropriate measure of central tendency for highly-skewed data distributions.
The variance is always greater than the standard deviation.
A 10% trimmed mean of a given data is solved by removing the largest 10% and smallest 10% of the data, then computing for the mean.
The coefficient of variation is the ratio between the mean and the standard deviation.

What is the meaning of percentile?
I am confused by the term percentile. Once my teacher told me that percentile means the percentage with respect to the score of the highest achiever.
This means that if in a competition I got $80$ out of $100$ and the highest score in that competition was 90 out of 100 then my percentile would be $\frac{80}{90}\ast 100=88.89$
So I got $80\mathrm{\%}$ and $88.89$ percentile.
I was believing that my above concept was right.
But when I see the definition of percentile on Wikipedia then I got something new (but I don't understand this definition) and then I thought that what my teacher told me was wrong.
Kindly tell me if my teacher right or wrong.

What are the slopes and $y$-coordinates of the $y$-intercepts of the following lines.
$a)y=-3x+2$
$b)2y=-3x+2$
$c)5y=2-3x$
$d)y+3x-2=0$
And as the slope intercept form is $y=mx+b$.

An engineering company has four openings and the applicant pool consists of 6 database administrators and eight network engineers. All are equally qualified so the hiring will be done randomly. The hiring committee consists of 4 women and 4 men.
a. If one person on the hiring committee is chosen at random to draw the names out of a hat, what is the probability that the person drawing the names is a woman.
b. How many ways can the group who are to be hired be formed if they are no restrictions on composition?
c. How many ways can 3 database administrators be chosen?

Find the mean, median, and mode of the given set of raw data. (If more than one mode exists, separate your answers with commas. If an answer does not exist, enter DNE.)
1.2 1.8 0.7 1.5 1.0 0.7 1.9 1.7 1.2
0.8 1.7 1.3 2.3 0.9 2.0 1.7 1.5 2.2
1.45
mean
median
mode

The following is the average daily temperature for Frederick, MaryLand for the month of June:
$$\begin{array}{|cccccc|}\hline 81& 78& 78& 89& 74& 85\\ 85& 84& 80& 90& 73& 86\\ 86& 82& 90& 92& 70& 73\\ 79& 92& 76& 74& 86& 76\\ 71& 81& 73& 77& 72& 79\\ \hline\end{array}$$
a) Complete the frequency distribution for the data.
$$\begin{array}{|ccc|}\hline Temperature& Frequency& RelativeFrequency\\ 70-74\\ 75-79\\ 80-84\\ 85-89\\ 90-94\\ \hline\end{array}$$