BSTAT Test 2

Which of the following meets the requirements of a stratified random sample?

A population contains 10 members under the age of 25 and 20 members over the age of 25. The sample will include two people chosen at random under the age of 25 and four people chosen at random over 25.

Let X be normally distributed with mean μ and standard deviation σ > 0. Which of the following is true about the z value corresponding to a given x value?

A positive z = (x - μ)/σ indicates how many standard deviations x is above μ. A negative z = (x - μ)/σ indicates how many standard deviations x is below μ. The z value corresponding to x = μ is zero.

The cumulative distribution function is denoted and defined as which of the following?

F(x) and F(x) = P(X ≤ x)

If a population is known to be normally distributed, what can be said of the sampling distribution of the sample mean drawn from this population?

For any sample size n, the sampling distribution of the sample mean is normally distributed.

Which of the following is not a form of bias?

Information from the sample is typical of information in the population.

A continuous random variable has the uniform distribution on the interval [a, b] if its probability density function f(x) ______

Is constant for all x between a and b, and 0 otherwise.

Which of the following statements is the most accurate about a binomial random variable?

It counts the number of successes in a given number of trials

What is a characteristic of the mass function of a discrete random variable X?

The sum of probabilities P(X = x) over all possible values x is 1. For every possible value x, the probability P(X = x) is between 0 and 1. Describes all possible values x with the associated probabilities P(X = x) .

Which of the following meets the requirements of a simple random sample?

population contains 10 members under the age of 25 and 20 members over the age of 25. The sample will include six people chosen at random, without regard to age.

Selection bias occurs when _____

portions of the population are excluded from the consideration for the sample

According to the central limit theorem, the distribution of the sample means is normal if _______.

the sample size n ≥ 30

Bias can occur in sampling. Bias refers to _______.

the tendency of a sample statistic to systematically over- or underestimate a population parameter

Nonresponse bias occurs when _______.

those responding to a survey or poll differ systematically from the nonrespondents

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

The number of customer arrivals to a bank between 10 am and 11 am

Which of the following can be represented by a discrete random variable?

The number of obtained spots when rolling a six-sided die

Which of the following can be represented by a continuous random variable?

The time of a flight between Chicago and New York