Statistical Inferences Answers

A normal distribution of data has a mean of 15 and a standard deviation of 4. How many standard deviations from the mean is 25?

A

0.16

B

0.4

C

2.5

D

6.25

1

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A normal distribution of data has a mean of 15 and a standard deviation of 4. How many standard deviations from the mean is 25?

A

0.16

B

0.4

C

2.5

D

6.25

1

About what percentage of the data lies within 2 standard deviations of the mean in a normal distribution?

A

47.5%

B

68%

C

95%

D

99.7%

2

What is the approximate area of the unshaded region under the standard normal curve below? Use the portion of the standard normal table given to help answer the question. z Probability0.000.50001.000.84132.000.97723.000.9987

A

0.02

B

0.16

C

0.18

D

0.82

2

What is the approximate area of the unshaded region under the standard normal curve below? Use the portion of the standard normal table given to help answer the question. z Probability0.000.50001.000.84132.000.97723.000.9987

A

0.02

B

0.16

C

0.18

D

0.82

2

If a data value in a normal distribution has a negative z-score, which of the following must be true?

A

The data value must be negative.

B

The data value must be positive.

C

The data value must be less than the mean.

D

The data value must be greater than the mean.

3

For a standard normal distribution, find the approximate value of . Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.250.59871.000.84131.250.89441.500.93321.750.9599

A

11%

B

39%

C

61%

D

89%

3

For a standard normal distribution, find the approximate value of . Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.250.59871.000.84131.250.89441.500.93321.750.9599

A

11%

B

39%

C

61%

D

89%

4

The times of the runners in a marathon are normally distributed, with a mean of 3 hours and 50 minutes and a standard deviation of 30 minutes. What is the probability that a randomly selected runner has a time less than or equal to 3 hours and 20 minutes? Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.500.69151.000.84132.000.97723.000.9987

A

16%

B

32%

C

34%

D

84%

4

What is the approximate area of the shaded region under the standard normal curve below? Use the portion of the standard normal table to help answer the question.zProbability0.000.50001.000.84132.000.97723.000.9987

A

0.16

B

0.68

C

0.82

D

0.84

4

What is the approximate area of the unshaded region under the standard normal curve below? Use the portion of the standard normal table given to help answer the question. z Probability0.000.50001.000.84132.000.97723.000.9987

A

0.14

B

0.16

C

0.86

D

0.98

5

About what percentage of the data lies within 2 standard deviations of the mean in a normal distribution?

A

47.5%

B

68%

C

95%

D

99.7%

5

The probability that a random variable is greater than or equal to z standard deviations from the mean in a standard normal distribution is p%. What can be said with certainty about the probability that the random variable is less than or equal to –z standard deviations from the mean?

A

The probability is less than p%.

B

The probability is equal to p%.

C

The probability is greater than p%.

D

The probability is not equal to p%.

6

For a standard normal distribution, find the approximate value of . Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.220.58710.320.62550.420.66280.440.67000.640.73890.840.79951.000.8413

A

16%

B

34%

C

66%

D

84%

8

For a standard normal distribution, which of the following variables always equals 0?

A

Mu

B

Sigma

C

x

D

z

9

The times of the runners in a marathon are normally distributed, with a mean of 3 hours and 50 minutes and a standard deviation of 30 minutes. What is the probability that a randomly selected runner has a time less than or equal to 3 hours and 20 minutes? Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.500.69151.000.84132.000.97723.000.9987

A

16%

B

32%

C

34%

D

84%

10

Which of the following probabilities is equal to approximately 0.2957? Use the portion of the standard normal table below to help answer the question.zProbability0.000.50000.250.59870.500.69150.750.77341.000.84131.250.89441.500.93321.750.9599

A

P (negative 1.25 less-than-or-equal-to z less-than-or-equal-to 0.25)

B

P (negative 1.25 less-than-or-equal-to z less-than-or-equal-to 0.75)

C

P (0.25 less-than-or-equal-to z less-than-or-equal-to 1.25)

D

P (0.75 less-than-or-equal-to z less-than-or-equal-to 1.25)

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Statistical Inferences Answers

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