 91.1: Define a population
 91.2: What kind of sample was used?
 91.3: Do you feel that it is representative?
 91.4: What are your hypotheses
 91.5: What significance level will you use?
 91.6: What statistical test will you use?
 91.7: What are the test results? (Assume s1 8.8 and s2 7.8.)
 91.8: What is your decision?
 91.9: What can you conclude?
 91.10: Do you feel that using the data given really answers the original q...
 91.11: What other data might be used to answer the question?
 91.1: Explain the difference between testing a single mean and testing th...
 91.2: When a researcher selects all possible pairs of samples from a popu...
 91.3: What two assumptions must be met when you are using the z test to t...
 91.4: Show two different ways to state that the means of two populations ...
 91.5: For Exercises 5 through 17, perform each of the following steps. a....
 91.6: For Exercises 5 through 17, perform each of the following steps. a....
 91.7: For Exercises 5 through 17, perform each of the following steps. a....
 91.8: For Exercises 5 through 17, perform each of the following steps. a....
 91.9: For Exercises 5 through 17, perform each of the following steps. a....
 91.10: For Exercises 5 through 17, perform each of the following steps. a....
 91.11: For Exercises 5 through 17, perform each of the following steps. a....
 91.12: For Exercises 5 through 17, perform each of the following steps. a....
 91.13: For Exercises 5 through 17, perform each of the following steps. a....
 91.14: For Exercises 5 through 17, perform each of the following steps. a....
 91.15: For Exercises 5 through 17, perform each of the following steps. a....
 91.16: For Exercises 5 through 17, perform each of the following steps. a....
 91.17: For Exercises 5 through 17, perform each of the following steps. a....
 91.18: Credit Card Debt The average credit card debt for a recent year was...
 91.19: Literacy Scores Adults aged 16 or older were assessed in three type...
 91.20: Battery Voltage Two brands of batteries are tested, and their volta...
 91.21: Exam Scores at Private and Public Schools A researcher claims that ...
Solutions for Chapter 91: Testing the Difference Between Two Means, Two Proportions, and Two Variances
Full solutions for Elementary Statistics: A Step by Step Approach  7th Edition
ISBN: 9780073534978
Solutions for Chapter 91: Testing the Difference Between Two Means, Two Proportions, and Two Variances
Get Full SolutionsChapter 91: Testing the Difference Between Two Means, Two Proportions, and Two Variances includes 32 full stepbystep solutions. This expansive textbook survival guide covers the following chapters and their solutions. This textbook survival guide was created for the textbook: Elementary Statistics: A Step by Step Approach, edition: 7. Elementary Statistics: A Step by Step Approach was written by Patricia and is associated to the ISBN: 9780073534978. Since 32 problems in chapter 91: Testing the Difference Between Two Means, Two Proportions, and Two Variances have been answered, more than 7629 students have viewed full stepbystep solutions from this chapter.

Additivity property of x 2
If two independent random variables X1 and X2 are distributed as chisquare with v1 and v2 degrees of freedom, respectively, Y = + X X 1 2 is a chisquare random variable with u = + v v 1 2 degrees of freedom. This generalizes to any number of independent chisquare random variables.

All possible (subsets) regressions
A method of variable selection in regression that examines all possible subsets of the candidate regressor variables. Eficient computer algorithms have been developed for implementing all possible regressions

Alternative hypothesis
In statistical hypothesis testing, this is a hypothesis other than the one that is being tested. The alternative hypothesis contains feasible conditions, whereas the null hypothesis speciies conditions that are under test

Attribute
A qualitative characteristic of an item or unit, usually arising in quality control. For example, classifying production units as defective or nondefective results in attributes data.

Axioms of probability
A set of rules that probabilities deined on a sample space must follow. See Probability

Central composite design (CCD)
A secondorder response surface design in k variables consisting of a twolevel factorial, 2k axial runs, and one or more center points. The twolevel factorial portion of a CCD can be a fractional factorial design when k is large. The CCD is the most widely used design for itting a secondorder model.

Coeficient of determination
See R 2 .

Consistent estimator
An estimator that converges in probability to the true value of the estimated parameter as the sample size increases.

Correction factor
A term used for the quantity ( / )( ) 1 1 2 n xi i n ? = that is subtracted from xi i n 2 ? =1 to give the corrected sum of squares deined as (/ ) ( ) 1 1 2 n xx i x i n ? = i ? . The correction factor can also be written as nx 2 .

Covariance matrix
A square matrix that contains the variances and covariances among a set of random variables, say, X1 , X X 2 k , , … . The main diagonal elements of the matrix are the variances of the random variables and the offdiagonal elements are the covariances between Xi and Xj . Also called the variancecovariance matrix. When the random variables are standardized to have unit variances, the covariance matrix becomes the correlation matrix.

Decision interval
A parameter in a tabular CUSUM algorithm that is determined from a tradeoff between false alarms and the detection of assignable causes.

Dispersion
The amount of variability exhibited by data

Distribution free method(s)
Any method of inference (hypothesis testing or conidence interval construction) that does not depend on the form of the underlying distribution of the observations. Sometimes called nonparametric method(s).

Error variance
The variance of an error term or component in a model.

Estimate (or point estimate)
The numerical value of a point estimator.

Experiment
A series of tests in which changes are made to the system under study

Fractional factorial experiment
A type of factorial experiment in which not all possible treatment combinations are run. This is usually done to reduce the size of an experiment with several factors.

Frequency distribution
An arrangement of the frequencies of observations in a sample or population according to the values that the observations take on

Gamma function
A function used in the probability density function of a gamma random variable that can be considered to extend factorials

Goodness of fit
In general, the agreement of a set of observed values and a set of theoretical values that depend on some hypothesis. The term is often used in itting a theoretical distribution to a set of observations.
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