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Answer: C) 81.5%</h3>
This value is approximate.
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Explanation:
We have a normal distribution with these parameters
- mu = 128 = population mean
- sigma = 30 = population standard deviation
The goal is to find the area under the curve from x = 68 to x = 158, where x is the number of text messages sent per day. So effectively, we want to find P(68 < x < 158).
Let's convert the score x = 68 to its corresponding z score
z = (x-mu)/sigma
z = (68-128)/30
z = -60/30
z = -2
This tells us that the score x = 68 is exactly two standard deviations below the mean mu = 128.
Repeat for x = 158
z = (x-mu)/sigma
z = (158-128)/30
z = 30/30
z = 1
This value is exactly one standard deviation above the mean
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The problem of finding P(68 < x < 158) can be rephrased into P(-2 < z < 1)
We do this because we can then use the Empirical rule as shown in the diagram below.
We'll focus on the regions between z = -2 and z = 1. This consists of the blue 13.5% on the left, and the two pink 34% portions. So we will say 13.5% + 34% + 34% = 81.5%
Approximately 81.5% of the the population sends between 68 and 158 text messages per day. This value is approximate because the percentages listed in the Empirical rule below are approximate.
The temperature which has best degree of precision would
actually be the temperature reading which has similar decimal place with the
error. So the best answer would have 1 decimal and from the choices above, this
would be:
D. 16.0°C
Any function is also a relation. The function shown in the graph can be described by ...
C. both a relation and a function
I think it b because 50 already and 35 each hour