We have a sample of 28 data points. The sample mean is 30.0 and the sample standard deviation is 2.40. The confidence level required is 98%. Then, we calculate α by:
The confidence interval for the population mean, given the sample mean μ and the sample standard deviation σ, can be calculated as:
Where n is the sample size, and Z is the z-score for 1 - α/2. Using the known values:
Where (from tables):
Finally, the interval at 98% confidence level is:
Given:
The system of inequalities:
To find:
The point that represents a solution to the system by using the graph.
Solution:
We have,
The related equations of these inequalities are:
The line is a vertical line that intersect the x-axis at 3.
The table of values for is:
x y
0 -5
1 -3
Plot (0,-5) and (1,-3) on a coordinate plan and connect them by a straight line.
The boundary lines are dotted lines because the points on the lines are not included in the solution set.
Check the inequalities for (0,0).
First inequality: ( False)
Second inequality:
(False)
Both inequalities are false for (0,0). It means the shaded region of the lines is in the opposite direction of (0,0).
Plot the shaded region and the points (-3, -1), (1, 11), (4, -1), (5, 6) as shown in the below graph.
From the below graph, it is clear that the point (4,-1) is the only point lies in the common shaded region. So, (4,-1) represents a solution to the system.
Therefore, the correct option is C.
