Stat-351 Chpt 7, 9e

Which of the following statements is correct regarding the percentile points of the F distribution?

F = 1/F

Bob took a biology exam whose mean was 70 with standard deviation 5. He also took a chemistry exam whose mean was 80 with standard deviation 10. He scored 85 on both exams. On which exam did he do better compared to the other students who took the exam?

He did better on the biology exam, comparatively speaking.

The Student t distribution:

Is symmetrical, approaches the normal distribution as the degrees of freedom increase, has more area in the tails than the standard normal distribution does.

Given that Z is a standard normal random variable, the area to the left of a value z is expressed as:

P(Z< or equal to z)

Which of the following distributions is not skewed?

Student t

Which of the following is not a characteristic for a normal distribution?

The mean is always zero.

A standard normal distribution is a normal distribution with:

a mean of zero and a standard deviation of one.

Which of the following does not represent a continuous uniform random variable?

f(x) = 1/3 for x= 4, 5, 6.

Which of the following is true about f(x) when X has a uniform distribution over the interval [a, b] ?

f(x) equals one divided by the length of the interval from a to b.

The probability density function, f(x), for any continuous random variable X, represents:

the height of the density function at x.

Most values of a standard normal distribution lie between:

-3 and 3

Suppose X has a chi-squared distribution with 10 degrees of freedom. The mean of X is:

10

What is the shape of the probability density function for a uniform random variable on the interval [a, b]?

All [A. A rectangle whose X values go from a to b.] [B. A straight line whose height is 1/(b-a) over the range [a, b]. [C. A continuous probability density function with the same value of f(x) from a to b. ]

Which of the following represents a difference between continuous and discrete random variables?

All [A. Continuous random variables assume an uncountable number of values, and discrete random variables do not.] [B. The probability for any individual value of a continuous random variable is zero, but for discrete random variables it is not.] [C. Probability for continuous random variables means finding the area under a curve, while for discrete random variables it means summing individual probabilities.]

Which of the following is always true for all probability density functions of continuous random variables?

All [A. The probability at any single point is zero.] [B. They contain an uncountable number of possible values.] [C. The total area under the density function f(x) equals 1]