Chapter 11: Problem 4
Determine the value of \(\chi^{2}\) for 14 degrees of freedom and an area of \(.10\) in the left tail of the chisquare distribution curve.
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Chapter 11: Problem 4
Determine the value of \(\chi^{2}\) for 14 degrees of freedom and an area of \(.10\) in the left tail of the chisquare distribution curve.
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A chemical manufacturing company wants to locate a hazardous waste disposal site near a city of 50,000 residents and has offered substantial financial inducements to the city. Two hundred adults (110 women and 90 men) who are residents of this city are chosen at random. Sixty percent of these adults oppose the site, \(32 \%\) are in favor, and \(8 \%\) are undecided. Of those who oppose the site, \(65 \%\) are women; of those in favor, \(62.5 \%\) are men. Using a \(5 \%\) level of significance, can you conclude that opinions on the disposal site are dependent on gender?
One of the products produced by Branco Food Company is Total-Bran Cereal, which competes with three other brands of similar total-bran cereals. The company's research office wants to investigate if the percentage of people who consume total-bran cereal is the same for each of these four brands. Let us denote the four brands of cereal by \(\mathrm{A}, \mathrm{B}, \mathrm{C}\), and \(\mathrm{D}\). A sample of 1000 persons who consume total-bran cereal was taken, and they were asked which brand they most often consume. Of the respondents, 212 said they usually consume Brand A, 284 consume Brand B, 254 consume Brand \(\mathrm{C}\), and 250 consume Brand D. Does the sample provide enough evidence to reject the null hypothesis that the percentage of people who consume total-bran cereal is the same for all four brands? Use \(\alpha=.05\).
A sample of 21 observations selected from a normally distributed population produced a sample variance of \(1.97 .\) a. Write the null and alternative hypotheses to test whether the population variance is greater than \(1.75\). b. Using \(\alpha=.025\), find the critical value of \(\chi^{2}\). Show the rejection and nonrejection regions on a chi-square distribution curve. c. Find the value of the test statistic \(\chi^{2}\). d. Using a \(2.5 \%\) significance level, will you reject the null hypothesis stated in part a?
A 2010 poll by Marist University asked people to choose their favorite classic Christmas movie from a list of five choices. The following table shows the frequencies for the various movies: $$ \begin{array}{l|ccccc} \hline & \text { It's A } & \text { A Christmas } & \text { Miracle on } & \text { White } & \text { A Christmas } \\ \text { Movie } & \text { Wonderful Life } & \text { Story } & \text { 34th Street } & \text { Christmas } & \text { Carol } \\ \hline \text { Frequency } & 247 & 237 & 226 & 124 & 134 \\ \hline \end{array} $$
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.
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