- 9.1: In Exercises 14, use the following survey results: Randomly selecte...
- 9.2: In Exercises 14, use the following survey results: Randomly selecte...
- 9.3: In Exercises 14, use the following survey results: Randomly selecte...
- 9.4: In Exercises 14, use the following survey results: Randomly selecte...
- 9.5: Listed below are the costs (in dollars) of repairing the front ends...
- 9.6: Refer to the sample data given in Exercise 5 and identify the null ...
- 9.7: When testing the hypotheses from Exercise 6, we get the test statis...
- 9.8: Which distribution is used to test the claim that the standard devi...
- 9.9: Determine whether the following statement is true or false: When te...
- 9.10: Determine whether the following statement is true or false: When us...
Solutions for Chapter 9: Inferences from Two Samples
Full solutions for Elementary Statistics | 12th Edition
The arithmetic mean of a set of numbers x1 , x2 ,…, xn is their sum divided by the number of observations, or ( / )1 1 n xi t n ? = . The arithmetic mean is usually denoted by x , and is often called the average
Bivariate normal distribution
The joint distribution of two normal random variables
In experimental design, a group of experimental units or material that is relatively homogeneous. The purpose of dividing experimental units into blocks is to produce an experimental design wherein variability within blocks is smaller than variability between blocks. This allows the factors of interest to be compared in an environment that has less variability than in an unblocked experiment.
A horizontal line on a control chart at the value that estimates the mean of the statistic plotted on the chart. See Control chart.
A subset selected without replacement from a set used to determine the number of outcomes in events and sample spaces.
Conditional probability distribution
The distribution of a random variable given that the random experiment produces an outcome in an event. The given event might specify values for one or more other random variables
Continuous random variable.
A random variable with an interval (either inite or ininite) of real numbers for its range.
A graphical display used to monitor a process. It usually consists of a horizontal center line corresponding to the in-control value of the parameter that is being monitored and lower and upper control limits. The control limits are determined by statistical criteria and are not arbitrary, nor are they related to speciication limits. If sample points fall within the control limits, the process is said to be in-control, or free from assignable causes. Points beyond the control limits indicate an out-of-control process; that is, assignable causes are likely present. This signals the need to ind and remove the assignable causes.
In regression, Cook’s distance is a measure of the inluence of each individual observation on the estimates of the regression model parameters. It expresses the distance that the vector of model parameter estimates with the ith observation removed lies from the vector of model parameter estimates based on all observations. Large values of Cook’s distance indicate that the observation is inluential.
A dimensionless measure of the linear association between two variables, usually lying in the interval from ?1 to +1, with zero indicating the absence of correlation (but not necessarily the independence of the two variables).
In hypothesis testing, this is the portion of the sample space of a test statistic that will lead to rejection of the null hypothesis.
Cumulative normal distribution function
The cumulative distribution of the standard normal distribution, often denoted as ?( ) x and tabulated in Appendix Table II.
Defects-per-unit control chart
See U chart
A subset of effects in a fractional factorial design that deine the aliases in the design.
Discrete random variable
A random variable with a inite (or countably ininite) range.
The amount of variability exhibited by data
Extra sum of squares method
A method used in regression analysis to conduct a hypothesis test for the additional contribution of one or more variables to a model.
A model that contains only irstorder terms. For example, the irst-order response surface model in two variables is y xx = + ?? ? ? 0 11 2 2 + + . A irst-order model is also called a main effects model
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.
A function used in the probability density function of a gamma random variable that can be considered to extend factorials