Stats final
Under what conditions can the t-distribution be correctly employed to test the difference between two population means?
- When the samples from the two populations are small and the population variances are unknown. - When the two populations of interest are assumed to be normally distributed. - When the population variances are assumed to be equal.
In a one-way ANOVA, which of the following is true?
-If the null hypothesis is rejected, it may still be possible that two or more of the population means are equal. -The degrees of freedom associated with the between sum of squares is equal to one less than the number of populations. -The critical value will be an F-value from the F distribution
Which of the following is an assumption for the one-way analysis of variance experimental design?
-The observations are independent. -All populations are normally distributed. -The populations have equal variances.
In performing chi-square contingency analysis, what will overcome a small expected cell frequency problem?
-To overcome a small expected cell frequency problem, increase the sample size. -To overcome a small expected cell frequency problem, combine the categories of the row and/or column variables.
In conducting a one-way analysis of variance where the test statistic is less than the critical value, which of the following is correct?
Conclude that all means are the same and there is no need to conduct the Tukey-Kramer procedure.
In a contingency analysis, the greater the difference between the actual and the expected frequencies, the more likely
Ho should be rejected
Based on the analysis of variance F-test, what conclusion should be reached regarding the null hypothesis? Test using a significance level of 0.01.
Since 14.667>2.8778, reject H0 and conclude that at least two populations means are different.
Which of the following is a correct interpretation for the regression slope coefficient?
The average change in y of a one-unit change in x will be b1 units.
Which of the following statements is true?
The decision maker controls the probability of making a Type I statistical error.
Which of the following would be an appropriate null hypothesis?
The mean of a population is equal to 55.
In a one-way design, which of the following is true?
The mean squares between will be larger than the mean squares within if the null hypothesis is rejected.
In order for a one-way analysis of variance to be considered a balanced design, which of the following must hold?
The sample sizes selected from each population must be equal.
Based upon this output, which of the following statements is true if the test is conducted at the 0.05 level of significance?
There is no basis for concluding that mean sales is different for the different days of the week.
If a manager wishes to develop a confidence interval estimate for estimating the difference between two population means, an increase in confidence level will result in which of the following conditions?
a wider confidence interval
A fixed effects analysis of variance differs from a random-effects analysis of variance in the way in which the sums of squares are computed.
false
A one-tailed hypothesis for a population mean with a significance level equal to .05 will have a critical value equal to z =.45.
false
Determine whether the following statement is True or False: If the sample size is large, the standard normal distribution can be used in place of the chi-square in a goodness-of-fit test for testing whether the population is normally distributed.
false
If any of the observed frequencies are smaller than 5, then categories should be combined until all observed frequencies are at least 5.
false
In a hypothesis test, the p-value measures the probability that the alternative hypothesis is true.
false
In a simple regression model, the slope coefficient represents the average change in the independent variable for a one-unit change in the dependent variable.
false
In a chi-square contingency analysis application, the expected cell frequencies will be equal in all cells if the null hypothesis is true.
false
In a one-tailed hypothesis test, the larger the significance level, the greater the critical value will be.
false
In conducting one-way analysis of variance, the sample size for each group must be equal.
false
Increasing the size of the samples in a study to estimate the difference between two population means will increase the level of confidence that a decision maker can have regarding the interval estimate.
false
The term one-way analysis of variance refers to the fact that in conducting the test, there is only one way to set up the null and alternative hypotheses.
false
The test statistic that is used when testing hypotheses about the difference between two population proportions is the t-value from the t-distribution.
false
The within sample variation is the dispersion that exists because the sample means for the various factor levels are not all equal.
false
The Tukey-Kramer method for multiple comparisons can only be used when the analysis of variance design is balanced.
false
To find a confidence interval for the difference between the means of independent samples, when the variances are unknown but assumed equal, the sample sizes of the two groups must be the same.
false
Under the basic logic of one-way analysis of variance, if the within variation is large relative to the between variation, it is an indication that the population means are likely to be different.
false
When performing a hypothesis test for the difference between the means of two independent populations where the standard deviations are known, it is necessary to use the pooled standard deviation in calculating the test statistic.
false
When testing a hypothesis involving population proportions, an increase in sample size will result in a smaller chance of making a Type I statistical error.
false
When using the t-distribution in a hypothesis test, the population does not need to be assumed normally distributed.
false
The Cresswell Company updates its annual sales forecast every month as new sales data becomes available. What is the one-month update called?
forecast interval
In a recent meeting, the marketing manager for a large hardware company stated that he needed to have a forecast prepared for the next three months. What is the three-month period called?
forecasting horizon
In a recent meeting, the sales manager for a drug company stated that she needed to have a forecast prepared for each week for the next six weeks. What is the week in this case?
forecasting period
If an economist wishes to determine whether there is evidence that average family income in a community near Seattle exceeds $125,000. What is an appropriate alternative hypothesis?
m > 125,000
When estimating a confidence interval for the difference between 2 means using the method where sample variances are pooled, which of the following assumptions is not needed?
the sample sizes are equal
A correlation coefficient computed from a sample of data values selected from a population is called a statistic and is subject to sampling error.
true
All other things held constant, decreasing the level of confidence for a confidence interval estimate for the difference between two population means will result in a smaller margin of error.
true
An article in an operations management journal recently stated that a formal hypothesis test rejected the hypothesis that mean employee productivity was less than $45.70 per hour in the wood processing industry. Given this conclusion, it is possible that a Type I statistical error was committed.
true
A goodness-of-fit test can be used to determine whether a set of sample data comes from a specific hypothesized population distribution.
true
A goodness-of-fit test can decide whether a set of data comes from a specific hypothesized distribution.
true
By combining cells we guard against having an inflated test statistic that could have led us to incorrectly reject the H0
true
Contingency analysis helps to make decisions when multiple proportions are involved.
true
Given this information, the proper design to test whether the means are equal is a one-way ANOVA balanced design.
true
If the test statistic for a chi-square goodness-of-fit test is larger than the critical value, the null hypothesis should be rejected.
true
If you are interested in estimating the difference between the means of two samples that have been paired, the point estimate for this difference is the mean value of the paired differences.
true
In a one-way analysis of variance design, the total variation in the data across the various factor levels can be partitioned into two parts, the within sample variation and the between sample variation.
true
In conducing one-way analysis of variance, the population distributions are assumed normally distributed.
true
In conducting a hypothesis test where the conclusion is to reject the null hypothesis, then either a correct decision has been made or else a Type I error.
true
Of the two types of statistical errors, the one that decision makers have most control over is Type I error.
true
The point estimate in a paired difference estimation example is an estimation of the population differences lying halfway between the interval limits of a confidence interval.
true
The significance level in a hypothesis test corresponds to the maximum probability that a Type I error will be committed.
true
The variance inflation factor is an indication of how much multicollinearity there is in the regression model.
true
The t-distribution is still applicable even when there are small violations of the assumptions for the case when the variances for two populations are unknown. This is particularly true when the sample sizes are approximately equal.
true
Type II error is failing to reject the null hypothesis when the null is actually false.
true
When someone has been accused of a crime the null hypothesis is: H0: innocent. In this case, a Type I error would be convicting an innocent person.
true
When the expected cell frequencies are smaller than 5, the cells should be combined in a meaningful way such that the expected cell frequencies do exceed 5.
true
A hypothesis test for the difference between two means is considered a two-tailed test under which of the following conditions?
when the null states that the population means are equal
