Using the z-distribution, it is found that the 95% confidence interval for the mean lifetime of this type of drill, in holes drilled, is (10.4, 13.94).
We are given the <u>standard deviation for the population</u>, hence, the z-distribution is used. The parameters for the interval is:
- Sample mean of
- Population standard deviation of
- Sample size of
.
The margin of error is:
In which z is the critical value.
We have to find the critical value, which is z with a p-value of 
, in which 
is the confidence level.
In this problem, 
, thus, z with a p-value of 
, which means that it is z = 1.96.
Then:
The confidence interval is the <u>sample mean plus/minutes the margin of error</u>, hence:
The 95% confidence interval for the mean lifetime of this type of drill, in holes drilled, is (10.4, 13.94).
A similar problem is given at brainly.com/question/22596713
Answer:
x = 3
Step-by-step explanation:
5 = 3x - 4
9 = 3x
x = 3
Answer: So for the 9.5% percent I'm not sure if you mean by 9.5% off the price or more for the price so Ill just do both
If you subtract $300 from 9.5% you get 271.5 US$
But if you add $300 to 9.5% you get 328.5 US$
The answer to this problem would be about 4 hours
A)
well, we know the elevator's rate is -20 f/s, ok, so every second, is dropping 20 feet, therefore, "y" is "distance from the ground floor", so when y = 0, meaning the distance to the ground floor is 0, so you ARE at the ground floor then.
and "x" is how many seconds you've been in the elevator.
now, she got in the elevator for 6 seconds, so, the elevator went down by 20 * 6, or 120 feet down, reason why the slope is negative, when she stopped, she was 350 feet away from the ground floor still though.
if the elevator went down 120 feet, and she's still 350 feet from the ground floor, that means she boarded the elevator at 120 + 350 feet, or 470 feet.
b)
