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91Ó°ÊÓ

Determine which of the following are true and which are false. Then, in complete sentences, justify your answers.

a. When the sample size is large, the mean of X¯is approximately equal to the mean of X.

b. When the sample size is large, X¯is approximately normally distributed.

c. When the sample size is large, the standard deviation of X¯is approximately the same as the standard deviation of X.

Short Answer

Expert verified

All the statements are true.

The statements a,b,c of the question are true.

Step by step solution

01

Part (a) Step 1: Given Information 

We need to find this statement is true or false. " When the sample size is large, the mean of X¯ is approximately equal to the mean of X."

02

Part (a) Step 2: Explanation 

When the sample size is big, the central limit theorem holds true. The sample mean is almost equal to X¯.

03

Part (b) Step 1: Given Information 

We need to find this statement is true or false. " When the sample size is large, X¯is approximately normally distributed."

04

Part (b) Step 2: Explanation 

When the sample size is big, the central limit theorem holds true. Then X¯has a roughly normal distribution.

05

Part (c) Step 1: Given Information 

We need to find the statement is true or false. " When the sample size is large, the standard deviation of X¯is approximately the same as the standard deviation of X."

06

Part (c) Step 2: Explanation 

When the sample size is big, the central limit theorem holds true. The standard deviation of X¯is hence roughly equal to the sample mean's standard deviation.

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Most popular questions from this chapter

A manufacturer produces 25-pound lifting weights. The lowest actual weight is 24 pounds, and the highest is 26 pounds. Each weight is equally likely so the distribution of weights is uniform. A sample of 100 weights is taken.

a) What is the distribution for the sum of the weights of 100 25-pound lifting weights?

b) Find P(Σx < 2,450).

The cost of unleaded gasoline in the Bay Area once followed an unknown distribution with a mean of \(4.59and a standard deviation of \)0.10. Sixteen gas stations from the Bay Area are randomly chosen. We are interested in the average cost of gasoline for the 16gas stations. The distribution to use for the average cost of gasoline for the 16gas stations is:

a.X¯~N(4.59,0.10)

b.X¯~N4.59,0.1016

c.X¯~N4.59,160.10

d.X¯~N4.59,160.10

M&M candies large candy bags have a claimed net weight of 396.9g. The standard deviation for the weight of the

individual candies is 0.017g. The following table is from a stats experiment conducted by a statistics class.

RedOrangeYellowBrownBlueGreen
0.751
0.735
0.883
0.696
0.881
0.925
0.841
0.895
0.769
0.876
0.863
0.914
0.856
0.865
0.859
0.855
0.775
0.881
0.799
0.864
0.784
0.8060.854
0.865
0.966
0.852
0.824
0.840
0.810
0.865
0.859
0.866
0.858
0.868
0.858
1.015
0.857
0.859
0.848
0.859
0.818
0.876
0.942
0.838
0.851
0.982
0.868
0.809
0.873
0.863


0.803
0.865
0.809
0.888


0.932
0.848
0.890
0.925


0.842
0.940
0.878
0.793


0.832
0.833
0.905
0.977


0.807
0.845

0.850


0.841
0.852

0.830


0.932
0.778

0.856


0.833
0.814

0.842


0.881
0.791

0.778


0.818
0.810

0.786


0.864
0.881

0.853


0.825


0.864


0.855


0.873


0.942


0.880


0.825


0.882


0.869


0.931


0.912





0.887

The bag contained 465candies and the listed weights in the table came from randomly selected candies. Count the weights.

a. Find the mean sample weight and the standard deviation of the sample weights of candies in the table.

b. Find the sum of the sample weights in the table and the standard deviation of the sum of the weights.

c. If 465M&Ms are randomly selected, find the probability that their weights sum to at least 396.9.

d. Is the Mars Company’s M&M labeling accurate?

NeverReady batteries has engineered a newer, longer lasting AAA battery. The company claims this battery has an average life span of 17 hours with a standard deviation of 0.8 hours. Your statistics class questions this claim. As a class, you randomly select 30 batteries and find that the sample mean life span is 16.7 hours. If the process is working properly, what is the probability of getting a random sample of 30 batteries in which the sample mean lifetime is 16.7 hours or less? Is the company’s claim reasonable?

Your company has a contract to perform preventive maintenance on thousands of air-conditioners in a large city. Based on service records from previous years, the time that a technician spends servicing a unit averages one hour with a standard deviation of one hour. In the coming week, your company will serve a simple random sample of 70 units in the city. You plan to budget an average of 1.1 hours per technician to complete the work. Will this be enough time?

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