Chapter 11: Problem 10
Explain the difference between the observed and expected frequencies for a goodness-of-fit test.
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Chapter 11: Problem 10
Explain the difference between the observed and expected frequencies for a goodness-of-fit test.
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An auto manufacturing company wants to estimate the variance of miles per gallon for its auto model AST727. A random sample of 22 cars of this model showed that the variance of miles per gallon for these cars is .62. Assume that the miles per gallon for all such cars are (approximately) normally distributed. a. Construct the \(95 \%\) confidence intervals for the population variance and standard deviation. b. Test at a \(1 \%\) significance level whether the sample result indicates that the population variance is different from \(.30\).
A random sample of 25 students taken from a university gave the variance of their GPAs equal to \(.19 .\) a. Construct the \(99 \%\) confidence intervals for the population variance and standard deviation. Assume that the GPAs of all students at this university are (approximately) normally distributed. b. The variance of GPAs of all students at this university was \(.13\) two years ago. Test at a \(1 \%\) significance level whether the variance of current GPAs at this university is different from \(13 .\)
Sandpaper is rated by the coarseness of the grit on the paper. Sandpaper that is more coarse will remove material faster. Jobs such as the final sanding of bare wood prior to painting or sanding in between coats of paint require sandpaper that is much finer. A manufacturer of sandpaper rated 220, which is used for the final preparation of bare wood, wants to make sure that the variance of the diameter of the particles in their 220 sandpaper does not exceed \(2.0\) micrometers. Fifty-one randomly selected particles are measured. The variance of the particle diameters is \(2.13\) micrometers. Assume that the distribution of particle diameter is approximately normal. a. Construct the \(95 \%\) confidence intervals for the population variance and standard deviation. b. Test at a \(2.5 \%\) significance level whether the variance of the particle diameters of all particles in 220-rated sandpaper is greater than \(2.0\) micrometers.
Describe the chi-square distribution. What is the parameter (parameters) of such a distribution?
A sample of seven passengers boarding a domestic flight produced the following data on weights (in pounds) of their carry-on bags. \(\begin{array}{lllllll}46.3 & 41.5 & 39.7 & 31.0 & 40.6 & 35.8 & 43.2\end{array}\) a. Using the formula from Chapter 3, find the sample variance, \(s^{2}\), for these data. b. Make the \(98 \%\) confidence intervals for the population variance and standard deviation. Assume that the population from which this sample is selected is normally distributed. c. Test at a \(5 \%\) significance level whether the population variance is larger than 20 square pounds.
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