Help picture below problem 18 will give brainlest
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Answer:
a) <em>t</em> ≥ 5
b) (see below)
Step-by-step explanation:
First, make note of the info you are given and what you're trying to do:
- at midnight, 5°C
- drops consistently 2°C per hour
- finding <em>t</em>
- <em>t </em>= # of hours past midnight when temp. was past -4°C
- put <em>t</em> on a number line
So, first, you need to find the first point at when the temperature goes past -4°C. Notice that the question is asking for past -4°C, not -4°C<em> and</em> past. This means we're not including -4°C.
Every hour, we're dropping by 2°C. You can draw a visual to better understand the situation. See the image below.
So we know that starting from 5 am, we are lower than -4°C.
This is 5 hours from midnight.
So <em>t</em> ≥ 5. This means that the number of hours past midnight when the temperature was colder than -4°C was 5 or more hours.
On the number line, draw a circle on 5 (between 4 and 6), but shade it in because it includes 5. Then, shade or highlight to the right of that circle to the end of the number line.
This shows that <em>t</em> is equal to or greater than 5.
Answer:
n=206
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".
The population proportion have the following distribution
Solution to the problem
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 99% of confidence, our significance level would be given by and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that , we can use as prior estimate of p 0.5, since we don't have any other info provided, and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
And replacing into equation (b) the values from part a we got:
And rounded up we have that n=206