Answer:
The 80% confidence interval for the the population mean nitrate concentration is (0.144, 0.186).
Critical value t=1.318
Step-by-step explanation:
We have to calculate a 80% confidence interval for the mean.
The population standard deviation is not known, so we have to estimate it from the sample standard deviation and use a t-students distribution to calculate the critical value.
The sample mean is M=0.165.
The sample size is N=25.
When σ is not known, s divided by the square root of N is used as an estimate of σM:

The degrees of freedom for this sample size are:

The t-value for a 80% confidence interval and 24 degrees of freedom is t=1.318.
The margin of error (MOE) can be calculated as:
Then, the lower and upper bounds of the confidence interval are:

The 80% confidence interval for the population mean nitrate concentration is (0.144, 0.186).
Answer:
Each boy recieved $25.25 each
Step-by-step explanation:
First, you add up all the money the 3 boys spent.
15+15+15=45
Then you add the sum of the equation to the amount all the boys had afterward.
45+30.75=75.75
Finally, you divide that product to 3 boys.
75.75/3=25.25
Therfore the answer is $25.25 each.
Answer:
it's A 10
Step-by-step explanation:
10+20= 30
so 15×2=30
5+10=15
2( = ×2
Answer:
8.3%
Step-by-step explanation:
Step-by-step explanation:
Since angles in the same segment are equal, Angle ABC (x) = Angle AOC.
Since Angles AOC and COD are supplementary, Angle AOC = 180° - 130° = 50°
Therefore x = 50°.