The following data give the ages (in years) of all six members of a family. 57 5
ID: 3179783 • Letter: T
Question
The following data give the ages (in years) of all six members of a family.
57
53
31
27
22
14
Let x denote the age of a member of this family. What is the probability P(x=22)?
Round your answer to three decimal places.
P(x=22)=
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Consider a large population with =70 and =12. Assuming nN0.05, find the mean and standard deviation of a sample mean, x¯, for a sample size of 20.
Round your answers to three decimal places.
x¯=
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A population has a normal distribution. A sample of size n is selected from this population. Describe the shape of the sampling distribution of the sample mean for the following case.
n=29
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The delivery times for all food orders at a fast-food restaurant during the lunch hour are normally distributed with a mean of 6.4 minutes and a standard deviation of 4.4 minutes. Let x¯ be the mean delivery time for a random sample of 15 orders at this restaurant. Calculate the mean and standard deviation of x¯.
Round your answers to two decimal places.
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The GPAs of all students enrolled at a large university have an approximately normal distribution with a mean of 3.02 and a standard deviation of 0.29. Find the probability that the mean GPA of a random sample of 20 students selected from this university is 3.07 or higher.
Round your answer to four decimal places.
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The GPAs of all students enrolled at a large university have an approximately normal distribution with a mean of 3.02 and a standard deviation of 0.29. Find the probability that the mean GPA of a random sample of 20 students selected from this university is 2.90 or lower.
Round your answer to four decimal places.
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The GPAs of all students enrolled at a large university have an approximately normal distribution with a mean of 3.02 and a standard deviation of 0.29. Find the probability that the mean GPA of a random sample of 20 students selected from this university is 2.94 to 3.08.
Round your answer to four decimal places.
57
53
31
27
22
14
Explanation / Answer
a.
Mean ( u ) =6.4
Standard Deviation ( sd )= 4.4/ Sqrt(n) = 1.1361
Number ( n ) = 15
Normal Distribution = Z= X- u / (sd/Sqrt(n) ~ N(0,1)
b.
P(X >= 3.07) = (3.07-3.02)/0.29/ Sqrt ( 20 )
= 0.05/0.065= 0.7711
= P ( Z >0.7711) From Standard Normal Table
= 0.2203
c.
P(X < 2.9) = (2.9-3.02)/0.29/ Sqrt ( 20 )
= -0.12/0.0648= -1.8505
= P ( Z <-1.8505) From Standard NOrmal Table
= 0.032
d.
To find P(a <= Z <=b) = F(b) - F(a)
P(X < 2.94) = (2.94-3.02)/0.29/ Sqrt ( 20 )
= -0.08/0.0648
= -1.2337
= P ( Z <-1.2337) From Standard Normal Table
= 0.10866
P(X < 3.08) = (3.08-3.02)/0.29/ Sqrt ( 20 )
= 0.06/0.0648 = 0.9253
= P ( Z <0.9253) From Standard Normal Table
= 0.82259
P(2.94 < X < 3.08) = 0.82259-0.10866 = 0.7139
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