Chapter 9: Problem 34
Briefly explain the conditions that must hold true to use the \(t\) distribution to make a test of hypothesis about the population mean.
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Chapter 9: Problem 34
Briefly explain the conditions that must hold true to use the \(t\) distribution to make a test of hypothesis about the population mean.
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In a Gallup poll conducted July \(7-10,2014,45 \%\) of Americans said that they actively try to include organic foods into their diets (www.gallup.com). In a recent sample of 2100 Americans, 1071 said that they actively try to include organic foods into their diets. Is there significant evidence at a \(1 \%\) significance level to conclude that the current percentage of all Americans who will say that they actively try to include organic foods into their diets is different from \(45 \%\) ? Use both the \(p\) -value and the critical-value approaches.
Consider the following null and alternative hypotheses: $$ H_{0}: \mu=60 \text { versus } \quad H_{1}: \mu>60 $$ Suppose you perform this test at \(\alpha=.01\) and fail to reject the null hypothesis. Would you state that the difference between the hypothesized value of the population mean and the observed value of the sample mean is "statistically significant" or would you state that this difference is "statistically not significant?" Explain.
What are the five steps of a test of hypothesis using the critical value approach? Explain briefly,
At Farmer's Dairy, a machine is set to fill 32 -ounce milk cartons. However, this machine does not put exactly 32 ounces of milk into each carton; the amount varies slightly from carton to carton but has an approximate normal distribution. It is known that when the machine is working properly, the mean net weight of these cartons is 32 ounces. The standard deviation of the milk in all such cartons is always equal to 15 ounce. The quality control inspector at this company takes a sample of 25 such cartons every week, calculates the mean net weight of these cartons, and tests the null hypothesis, \(\mu=32\) ounces, against the altemative hypothesis, \(\mu \neq 32\) ounces. If the null hypothesis is rejected, the machine is stopped and adjusted. A recent sample of 25 such cartons produced a mean net weight of \(31.93\) ounces. a. Calculate the \(p\) -value for this test of hypothesis. Based on this \(p\) -value, will the quality control inspector decide to stop the machine and adjust it if she chooses the maximum probability of a Type I error to be .01? What if the maximum probability of a Type I error is 05 ? b. Test the hypothesis of part a using the critical-value approach and \(\alpha=.01\). Does the machine need to be adjusted? What if \(a=.05 ?\)
Explain which of the following is a two-tailed test, a left-tailed test, or a right-tailed test. a. \(H_{0}: \mu=12, H_{1}: \mu<12\) b. \(H_{0}: \mu \leq 85, H_{1}: \mu>85\) c. \(H_{0}: \mu=33, H_{1}: \mu \neq 33\) Show the rejection and nonrejection regions for each of these cases by drawing a sampling distribution curve for the sample mean, assuming that it is normally distributed.
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