(the question must tell you that a,b∈R)
a-1=5
b+3=8
a=6
b=5
Answer:
The 98% confidence interval for the mean amount spent on their child's last birthday gift is between $40.98 and $43.02.
Step-by-step explanation:
We have the standard deviation for the sample, which means that the t-distribution is used to solve this question.
The first step to solve this problem is finding how many degrees of freedom, we have. This is the sample size subtracted by 1. So
df = 24 - 1 = 23
98% confidence interval
Now, we have to find a value of T, which is found looking at the t table, with 23 degrees of freedom(y-axis) and a confidence level of
. So we have T = 2.5
The margin of error is:

In which s is the standard deviation of the sample and n is the size of the sample.
The lower end of the interval is the sample mean subtracted by M. So it is 42 - 1.02 = $40.98.
The upper end of the interval is the sample mean added to M. So it is 42 + 1.02 = $43.02.
The 98% confidence interval for the mean amount spent on their child's last birthday gift is between $40.98 and $43.02.
Answer: 
Step-by-step explanation:
1. You know that:
- The roped-off area whose width is represented with <em>x,</em> it is created around a rectangular museum.
- The dimensions of the rectangular museum are: 30 ft by 10 ft.
- The combined area of the display and the roped-off area is 800 ft².
2. The area of the rectangular museum can be calculated with:

Where
is the lenght and
is the width.
You have that the lenght and the width in feet are:

3. Let's call
the width of the roped-off area. Then, the combined area is:

Where



4. Substitute values and simplify. Then:


Divide both sides by 5
e^x=3.152 take the natural log of both sides...
x=ln(3.152)
x≈1.148
The answer is that x equals 15