A refrigerator operates on average for 10.0 hours an day. If the power rating is the refrigerator is 709 w how much electrical e
1 answer:
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Answer:
a) Sample size = 1691
b) 95% Confidence Interval = (0.3696, 0.4304)
Explanation:
(a) How large a sample n should they take to estimate p with 2% margin of error and 90% confidence?
The margin of error is given by
Where z is the corresponding z-score for 90% confidence level
z = 1.645 (from z-table)
for p = 0.50 and 2% margin of error, the required sample size would be
(b) The advocacy group took a random sample of 1000 consumers who recently purchased this mobile phone and found that 400 were happy with their purchase. Find a 95% confidence interval for p.
The sample proportion is
p = 400/1000
p = 0.40
z = 1.96 (from z-table)
n = 1000
The confidence interval is given by
Therefore, we are 95% confident that the proportion of consumers who bought the newest generation of mobile phone were happy with their purchase is within the range of (0.3696, 0.4304)
What is Confidence Interval?
The confidence interval represents an interval that we can guarantee that the target variable will be within this interval for a given confidence level.
Answer:
Explanation:
We can assume that the general formula for the drag force is given by:
And we can see that is proportional to the area. On this case we can calculate the area with the product of the width and the height. And we can express the grad force like this:
Where w is the width and h the height.
The last formula is without consider the area of the carrier, but if we use the area for the carrier we got:
If we want to find the additional power added with the carrier we just need to take the difference between the multiplication of drag force by the velocity (assuming equal velocities for both cases) of the two cases, and we got:
We can assume the same drag coeeficient and we got:
1.7 ft =0.518 m
60 mph = 26.822 m/s
In order to find the drag coeffcient we ned to estimate the Reynolds number first like this:
And the value for the kinematic vicosity was obtained from the table of physical properties of the air under standard conditions.
Now we can find the aspect ratio like this:
And we can estimate the calue of from a figure.
And we can calculate the power difference like this: