[2008] Topic 5: Some Important Probability Distributions 相关习题 following, statements, standard, outside

aianjie

 

AIM 1: Describe the key properties of the normal distribution, the standard normal distribution.

1、Which of the following statements about the normal probability distribution is most accurate?

A) The normal curve is asymmetrical about its mean.

B) The standardized normal distribution has a mean of zero and a standard deviation of 10.

C) Five percent of the normal curve probability falls more than outside two standard deviations from the mean. 

D) Sixty-eight percent of the area under the normal curve falls between 0 and +1 standard deviations above the mean.

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aianjie

 

The correct answer is A

Student’s t-distribution is defined by a single parameter known as the degrees of freedom

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AIM 5: Explain the degree of freedom

1、With 60 observations, what is the appropriate number of degrees of freedom to use when carrying out a statistical test on the mean of a population?

A) 61.

B) 60.

C) 58.

D) 59.

aianjie

 

The correct answer is D

When performing a statistical test on the mean of a population based on a sample of size n, the number of degrees of freedom is n – 1 since once the mean is estimated from a sample there are only n – 1 observations that are free to vary. In this case the appropriate number of degrees of freedom to use is 60 – 1 = 59.

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2、Which one of the following distributions is described entirely by the degrees of freedom?

A) Student’s t-distribution.

B) Normal distribution.

C) Binomial distribution.

D) Lognormal distribution.