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).
5% of $55 is $2.75 so the total should be $57.75??
Answer:
132,600 possibilities
Step-by-step explanation:
The first one chosen can be 1 of 52
The 2nd one chosen is 1 out 51
And the 3rd chosen is 1 out 50
So...
52 x 51 x 50 = 132,600