Complete question:
The manager of a supermarket would like to determine the amount of time that customers wait in a check-out line. He randomly selects 45 customers and records the amount of time from the moment they stand in the back of a line until the moment the cashier scans their first item. He calculates the mean and standard deviation of this sample to be barx = 4.2 minutes and s = 2.0 minutes. If appropriate, find a 90% confidence interval for the true mean time (in minutes) that customers at this supermarket wait in a check-out line
Answer:
(3.699, 4.701)
Step-by-step explanation:
Given:
Sample size, n = 45
Sample mean, x' = 4.2
Standard deviation
= 2.0
Required:
Find a 90% CI for true mean time
First find standard error using the formula:




Standard error = 0.298
Degrees of freedom, df = n - 1 = 45 - 1 = 44
To find t at 90% CI,df = 44:
Level of Significance α= 100% - 90% = 10% = 0.10

Find margin of error using the formula:
M.E = S.E * t
M.E = 0.298 * 1.6802
M.E = 0.500938 ≈ 0.5009
Margin of error = 0.5009
Thus, 90% CI = sample mean ± Margin of error
Lower limit = 4.2 - 0.5009 = 3.699
Upper limit = 4.2 + 0.5009 = 4.7009 ≈ 4.701
Confidence Interval = (3.699, 4.701)
Let B be the event that Andrea passes her test, and let A be the event
<span>that she studies. We are given that P(A and B) = 17/20, and that P(A) = 15/16. </span>
<span>Now the probability that Andrea passes her test given that she has studied </span>
<span>is represented by P(BlA). The formula your teacher gave you can be written as </span>
<span>P(BlA) = P(A and B) / P(A). </span>
<span>So P(BlA) = P(A and B) / P(A) = (17/20) / (15/16) = (17/20)*(16/15) = 68/75.</span>
Hi!
1/4 of 20 pencils are 5 pencils.
Since he gave away 4 pencils,
Total = 5 + 4 = 9
Mr. Simms use and give away total 9 pencils.
The answer is 6*square rooted*2
Triangle ABC is translated 3 units right and 2 units up
by looking at point A (-4,5) which is translated to A'(-1,7)
we can tell by looking at the points that -4 is shifted by 3 units to the right ti reach -1 and 5 is shifted upwards by 2 units to reach 7