Stats Exam
when the population has a normal distribution, the sampling distribution of the mean is normally distributed
for any sample size
in determining an interval estimate of a population mean then the stdev is unknown, we use a t distribution with ____ degrees of freedom
n-1
as the degrees of freedom increase, the t distribution approaches the
normal distribution
we can use the normal distribution to make confidence interval estimates for the population proportion, p, when
np>_ 5 and n (1-p) >_ 5
The standard error of the proportion will become larger as
p approaches 0.5
if we went to provide a 95% confidence interval for the mean of a population, the confidence coefficient is
.95
10. A normal probability distribution _____. a. is a continuous probability distribution b. is a discrete probability distribution c. can be either continuous or discrete d. always has a standard deviation of 1
a
12. In a standard normal distribution, the range of values of z is from _____. a. minus infinity to infinity b. -1 to 1 c. 0 to 1 d. -3.09 to 3.09
a
A continuous random variable may assume a. any value in an interval or collection of intervals b. only integer values in an interval or collection of intervals c. only fractional values in an interval or collection of intervals d. only the positive integer values in an interval
a
A description of how the probabilities are distributed over the values the random variable can assume is called a. probability distribution b. probability function c. random variable d. expected value
a
In a binomial experiment the a. probability of success does not change from trial to trial b. probability of success does change from trial to trial c. probability of success could change from trial to trial depending on the situation under consideration d. all of the answers are correct
a
The weight of an object, measured in grams, is an example of a. a continuous random variable b. a discrete random variable c. either a continuous or a discrete random variable, depending on the weight of the object d. either a continuous or a discrete random variable, depending on the units of measurement
a
an interval estimate is used to estimate
a population parameter
. The Poisson probability distribution is used with _____. a. a continuous random variable b. a discrete random variable c. either a continuous or discrete random variable d. any random variable
b
. The form of the continuous uniform probability distribution is _____. a. triangular b. rectangular c. bell-shaped d. a series of vertical lines
b
13. The exponential probability distribution is used with _____. a. a discrete random variable b. a continuous random variable c. any probability distribution with an exponential term d. an approximation of the binomial probability distribution
b
9. The mean, median, and mode have the same value for which of the following probability distributions? a. uniform b. normal c. exponential d. Poisson
b
The number of customers who enter a store during one day is an example of a. a continuous random variable b. a discrete random variable c. either a continuous or a discrete random variable, depending on the number of customers d. either a continuous or discrete random variable, depending on the gender of the customers
b
The expected value of a discrete random variable a. is the most likely or highest probability value for the random variable b. will always be one of the values x can take on, although it may not be the highest probability value for the random variable c. is the average value for the random variable over many repeats of the experiment d. all of the answers are correct
c
11. If the mean of a normal distribution is negative, _____. a. the standard deviation must also be negative b. the variance must also be negative c. a mistake has been made in the computations, because the mean of a normal distribution cannot be negative d. None of the answers is correct.
d
14. The expected value of equals the mean of the population from which the sample is drawn _____. a. only if the sample size is 30 or greater b. only if the sample size is 50 or greater c. only if the sample size is 100 or greater d. for any sample size
d
15. The standard deviation of is referred to as the _____. a. standard proportion b. sample proportion c. average proportion d. standard error of the proportion
d
from a population that is not normally distributed and whose standard deviation is not known, a sample of 50 items is selected to develop an interval estimate for m, what statement is true
the t distribution with 49 degrees of freedom must be used