Suppose that the average time spent per day with digital media several years ago was 3 hours and 22 minutes. For last​ year, a random sample of 20 adults in a certain region spent the numbers of hours per day with digital media given in the accompanying table. Preliminary data analyses indicate that the​ t-interval procedure can reasonably be applied. Find and interpret a 90​% confidence interval for last​ year's mean time spent per day with digital media by adults of the region.​ (Note: x=5.88hr and s=2.27​hr.)   The 90​% confidence interval is from ( ? ) ​hour(s) to ( ? )​hour(s).  Interpret the 90​% confidence interval. Select all that apply.     A. There is a 90​% chance that the mean amount of time spent per day on digital media last year by all adults in the region is between the​ interval's bounds.   B.With 90​% ​confidence, the mean amount of time spent per day on digital media last year by all adults in the region is between the​ interval's bounds.   C.90​% of all possible random samples of 20 adults in the region have mean amounts of time spent per day on digital media last year that are between the​ interval's bounds.   D. 90​% of all adults in the region spent amounts of time per day on digital media last year that are between the​ interval's bounds.

MATLAB: An Introduction with Applications
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Author:Amos Gilat
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1 Suppose that the average time spent per day with digital media several years ago was 3 hours and 22 minutes. For last​ year, a random sample of 20 adults in a certain region spent the numbers of hours per day with digital media given in the accompanying table. Preliminary data analyses indicate that the​ t-interval procedure can reasonably be applied. Find and interpret a
90​% confidence interval for last​ year's mean time spent per day with digital media by adults of the region.​ (Note: x=5.88hr and s=2.27​hr.)
 
The 90​% confidence interval is from ( ? ) ​hour(s) to ( ? )​hour(s).
 Interpret the 90​% confidence interval. Select all that apply.
 
 
A. There is a 90​% chance that the mean amount of time spent per day on digital media last year by all adults in the region is between the​ interval's bounds.
 
B.With 90​% ​confidence, the mean amount of time spent per day on digital media last year by all adults in the region is between the​ interval's bounds.
 
C.90​% of all possible random samples of 20 adults in the region have mean amounts of time spent per day on digital media last year that are between the​ interval's bounds.
 
D. 90​% of all adults in the region spent amounts of time per day on digital media last year that are between the​ interval's bounds.
 
3 Based on a recent​ study, the pH level of the arterial cord​ (one vessel in the umbilical​ cord) is normally distributed with mean7.23 and standard deviation of 0.11. Find the percentage of preterm infants who have the  following arterial cord pH levels.
 
a. pH levels between 7.00 and 7.50.
​(Round to two decimal places as​ needed.)
b. pH levels over 7.31.
​(Round to two decimal places as​ needed.)
 
4. A variable of a population has a mean of μ=81 and a standard deviation of σ=7. a. Identify the sampling distribution of the sample mean for samples of size 49.
b. In answering part​ (a), what assumptions did you make about the distribution of the​ variable?
 
What is the mean of the sampling​ distribution?
 
What is the standard deviation of the sampling​ distribution?
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