Bus 230 Econ Stats Ole Miss
The sample variance is always ______ as the population variance.
larger, smaller, or the same
The most important statistical descriptive measure of the location of a data set is the _____.
mean
List the three measures of central location:
mean, median, mode
The value which has half of the observations above it and half the observations below it is called the
median
The variance of a small of 169 observations equals 576. The standard deviation of the sample equals
24 (square root of 576)
The 75th percentile is referred to as the
3rd quartile.
The height (in inches) of 25 individuals were recorded and the following statistics were calculated: mean = 70 mode = 73 median = 74 range = 20 variance = 784 The coefficient of variation equals ______.
40% (CV = s//x * 100) CV = 28/70 * 100 = 40%
If the coefficient of variation is 40% and the mean is 70, then the variance is equal to _____.
784 CV = s // x * 100 .4 = s / 70 so... s = 28 s^2 = 784
The variance of a sample of 81 observations equals 64. The standard deviation of the sample equals ______.
8 (square root of 64)
A production process produces 2% defective parts. A sample of 5 parts from the production process is selected. What is the probability that the sample contains exactly 2 defective parts?
(n/x) p^x (1 - p)^n-x (5/2) .02^2 (.98)^3 10 * .0004 * .9412 =.0037
If you are conducting an experiment where the probability of a success is .02 and you are interested in the probability of 4 successes in 15 trials, the correct probability function use is the ______ distribution.
Binomial
A probability distribution showing the probability of 'x' successes in 'n' trials, where the probability of success does not change from trial to trial, is termed a _______.
Binomial "probability does not change"
When sampling without replacement, the probability of obtaining a certain sample is best given by a _______ distribution.
Hypergeometric
What are two numerical measures of the linear association between two variables?
Sxy, rxy
In the textile industry, a manufacturer is interested in the number of blemishes or flaws occurring in each 100 ft of material. The probability distribution that has the greatest chance of applying to this situation is the ______ distribution.
Poisson
The interquartile range is
Q3 - Q1
Another name for the mean of a distribution is ______.
expected value
List two conditions required for a discrete probability function.
f(x) is > or = 0 f(x) is < or = 1 Sum f(x) = 1
The coefficient of correlation can never be ______.
greater than 1 less than 1
Since the mode is the most frequently occurring data value, it is always _____ than the mean.
greater than, less than, or equal to
Since the population is always larger than the sample size, then the sample statistic is always _____ compared to the population parameter.
greater than, less than, or equal to
A numerical description of the outcome of an experiment is called a ______.
random variable
The measure of dispersion that is influenced most by extreme values is the ______.
range
The difference between the largest and the smallest data values is the
range.
When the data are skewed to the right, the longer tail of the distribution is on the _____.
right
The variance is a measure of dispersion or variability of a random variable. It is a weighted average of ______ of the mean.
squared deviations (from the mean)
The sum of deviations of the individual data elements from their mean is always ______.
zero
Standard deviation = 8 Coefficient of variation = 64% The mean would then be ______.
12.5 .64 = 8 / /x /x = 12.5
If a data set has an even number of observations, the median is calculated in two steps:
1. Put in order 2. Take the average of the middle two
The number of electrical outages in a city varies from day to day. Assume that the number of electrical outages (x) in the city has the following probability distribution. x f(x) o .80 1 .15 2 .04 3 .01 Find the mean and standard deviation.
E(x) = .26 Var(x) = .3329 sd(x) = .557
What symbol represents the mean of the population?
M
What symbol represents the size of the population?
N
A continuous random variable may assume ______ in an interval.
any value
The median is a measure of
central location.
The weight of an object is an example of _______ random variable.
continuous (infinite number of results)
The binomial probability distribution is used with a _______ random variable.
discrete
An experiment consists of making 80 telephone calls in order to sell a particular insurance policy. The random variable in this experiment is a _______ random variable.
discrete (countable results)
List three characteristics of the binomial probability distribution.
discrete 2 outcomes draw with replacement probability does not change independent outcomes
List 3 characteristics of the hypergeometric probability distribution.
discrete 2 outcomes draw without replacement probability does not change dependent outcomes
List 2 characteristics of the Poisson.
discrete time or distance
The Poisson probability distribution is used with a ______ random variable that involves _________ or _______.
discrete; time or distance
What symbol represent the size of the sample?
n
In computing the mean of a sample, the value of Sum(xi) is divided by
n (sample size)
The variance can never be ______.
negative
The variance of the sample can never be _____.
negative
The mean of a sample is computed by summing _______ and then dividing by _______.
values of xi; n (sample size)
List the four measures of dispersion:
variance standard deviation range IQR
The descriptive measure of dispersion that is based on the concept of a deviation about the mean is
variance. (check the notes for the formula)
The symbol for population variance is
weird O thing squared (o2)