Answer:
1. Three things influence the margin of error in a confidence interval estimate of a population mean: sample size, variability in the population, and confidence level. For each of these quantities separately, explain briefly what happens to the margin of error as that quantity increases.
Answer: As sample size increases, the margin of error decreases. As the variability in the population increases, the margin of error increases. As the confidence level increases, the margin of error increases. Incidentally, population variability is not something we can usually control, but more meticulous collection of data can reduce the variability in our measurements. The third of these—the relationship between confidence level and margin of error seems contradictory to many students because they are confusing accuracy (confidence level) and precision (margin of error). If you want to be surer of hitting a target with a spotlight, then you make your spotlight bigger.
Answer:
(a) 
(b) 7 hours.
Step-by-step explanation:
(a) Let x be the number of hours and y is the total cost.
We have been given that Beatrice and her friends charge $8 per hour of babysitting, so the charges for x hours of babysitting will be 8x.
As they also charge a mandatory $5 per day fee for each child for snacks, so the total charges for babysit each day will be charges for x hours of babysitting plus mandatory charge.
We can represent this information in an equation as:

Therefore, the equation
represents the total cost of using Beatrice’s babysitting service each day.
(b) To find the number of hours Beatrice babysit the daughter, we will substitute y = 61 in our equation and solve for x.

Let us subtract 5 from both sides of our equation.


Let us divide both sides of our equation by 8.


Therefore, Beatrice babysit 7 hours the daughter.
Expression for part c is missing.