Using the t-distribution to build the 99% confidence interval, it is found that:
- The margin of error is of 3.64.
- The 99% confidence interval for the population mean is (19.36, 26.64).
<h3>What is a t-distribution confidence interval?</h3>
The confidence interval is:

In which:
is the sample mean.
- s is the standard deviation for the sample.
The critical value, using a t-distribution calculator, for a two-tailed 95% confidence interval, with 21 - 1 = 20 df, is t = 2.086.
The other parameters are given as follows:

The margin of error is given by:

Hence the bounds of the interval are:


The 99% confidence interval for the population mean is (19.36, 26.64).
More can be learned about the t-distribution at brainly.com/question/16162795
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Answer:
20.0%
Step-by-step explanation:
The last 30 presidents of America starts from the 16th president, Abraham Lincoln and ends with the current and 45th president, Donald Trump.
The presidents that are 60 and above years during this period include
Donald Trump, Goerge H. W. Bush, Roland Regan, Gerald Ford, Dwight D. Eisenhower and Harry S. Truman.
Making 6 of them out of 30
The percentage is given by
Number of presidents aged 60 and above×100/Total number of presidents
6×30/100=20%
<span>$ 3,450.00
</span>Equation:
A = P(1 + rt)
Given:
Consider the equation is:

Some steps of the solution are given.
To find:
The next step of the solution.
Solution:
Step 1: The given equation is:

Step 2: Simplifying right hand side.

Step 3: Simplifying left hand side.

These steps are already given. So, the next step is:
Step 4: Subtracting 3 from both sides.

Therefore, the correct option is (b).
A(14)=240(1+0.09)^14-1
A(14)=240(1.09)^13
A(14)=240(3.065)
A(14)=735.79
Make sure the calculations m