a town had about 2120 acres of pine trees 40 years ago. Only about 13% of the pine trees remain. How many acres of pine trees re
2 answers:
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Answer:
f(x)=x^2+9x-10
Step-by-step explanation:
<u>Standard Form of Quadratic Function</u>
The standard form of a quadratic function is:
where a,b, and c are constants.
The factored form of a quadratic equation is:
Where and
are the roots or zeros of f, and a is constant.
We know the zeros of the function are 1 and -10. The function is:
Operating:
Joining like terms:
Since we are not given any more restrictions, we can choose the value of a=1, thus. the required function is:
Answer:
So on this case the 90% confidence interval would be given by (-0.30;2.50)
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 for the sample
population mean (variable of interest)
s=4.9 represent the sample standard deviation
n=51 represent the sample size
Solution to the problem
The confidence interval for the mean is given by the following formula:
(1)
In order to calculate the critical value we need to find first the degrees of freedom, given by:
Since the Confidence is 0.90 or 90%, the value of and
, and we can use excel, a calculator or a table to find the critical value. The excel command would be: "=-T.INV(0.05,50)".And we see that
Now we have everything in order to replace into formula (1):
So on this case the 90% confidence interval would be given by (-0.30;2.50)