X>-4 would be the correct answer
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Answer:
Speed = 20 mi/h
Explanation:
There are two points A and B
Distance between both the points are define with function -20t + 45 miles
where t represent the number of hours of travelling.
Now firstly we find the initial position. At starting time is 0, so we put t=0 in given function of t.
At t=0;
d₀ = -20(0) + 45 = 0 + 45 = 45 miles
Now we find the distance travell after starting first hour.
Than we put t = 1 in the given function
At t = 1;
d₁ = -20(1) + 45 = -20 + 45 = 25 miles
Difference between d₁ & d₀ is
45 - 25 = 20 miles
We see that in one hour, total distace is covered 20 miles
Now we use time, speed, distance relation
Speed = 
S = 
S = 20 miles/hour
That's the final answer.
I hope it will help you.
Answer:
Confidence Interval for the mean
Step-by-step explanation:
Confidence interval is made using the observations of a <em>sample</em> of data obtained from a population, so it is constructed in such a way, that, with a certain <em>level of confidence </em>(this is the statement mentioned in the question), that is, one could have a percentage of probability that the interval, or range around the value obtained, frequently 95%, contains the true value of a population parameter (in this case, the population mean).
It is one way to extract information from a population using a sample of it. This kind of information is what inference statistic is always looking for.
An <u>approximation</u> about how to construct this interval or range:
- Select a random sample.
- For the specific case of a <em>mean</em>, you need to calculate the mean of the <em>sample </em>(sample mean), and, if standard deviation is unknown or not mentioned, also calculate the sample standard deviation.
- With this information, and acknowledged that these values follows a standard normal distribution (a normal distribution with mean 0 and a standard deviation of 1), represented by random variable Z, one can use all this information to calculate a <em>confidence interval for the mean</em>, with a certain confidence previously choosen (for example, 95%), that the population mean must be in this interval or <em>range around this sample mean.</em>
