Answer:
Step-by-step explanation:
We are given the following in the question:
Keith has $100 in a savings account at the beginning of the summer.
Let x be the number of weeks he works.
He makes $25 each week at his babysitting job.
He wants to earn more than $350 dollars during summer.
Total money earned by job =
His total money in account should be more than 350$.
We can write this with the help of inequality:
The following inequality represents the given situation.
Answer:
So on this case the 85% confidence interval would be given by (7.2;7.4)
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
represent the sample mean
population mean (variable of interest)
represent the population standard deviation
n=830 represent the sample size
Solution to the problem
The confidence interval for the mean is given by the following formula:
(1)
Since the Confidence is 0.85 or 85%, the value of and
, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-NORM.INV(0.075,0,1)".And we see that
Now we have everything in order to replace into formula (1):
So on this case the 85% confidence interval would be given by (7.2;7.4)