The inspection division of the Lee County Weights and Measures Department is interested in estimating the actual amount of soft drink that is placed in 2-liter bottles at the local bottling plant of a large nationally known soft-drink company. The bottling plant has informed the inspection division that the standard deviation for 2-liter bottles is 0.05 liter, i.e. the population standard deviation is σ = 0.05. A random sample of one hundred 2-liter bottles obtained from this bottling plant indicates a sample average of 1.99 liters.
1. [5 points] Set up a 95% confidence interval estimate of the true average amount of soft drink in each bottle. What is the margin of error?
2. [4 points] Based on your answer to part 1, can we reject the null hypothesis H0 : µ = 2 vs. HA : µ ≠ 2 at a 95% confidence level? Explain.
3. [5 points] What would be your answer to previous question if n = 121? What about if n = 81? What is the range of the sample size such that the above hypothesis is rejected?
4. [8 points] Suppose now that Lee County requires these measurements in ounces instead (1 liter=33.8 ounces). Call this variable Y , that is Y = 33.8X. (a) [2 points] What is the mean of the sample in ounces? (Recall x¯ = 1.99) (b) [2 points] Whatisthe standard deviation ofthe population in ounces? I.e. whatisσy?(Recall σx =0.05) (c) [4 points] What is the margin of error for a 95% confidence interval for the amount of soft drink in a bottle in ounces? Compare your answer to the one in part 1. Hint: Compare the ratio of the margin of errors, using the one for ounces in the numerator. ∗
5. [8points]Let's go back to liters.Assume that we no longer haveσ but we calculateds=0.048 fromthe sample. (a) [3 points] Construct the test statistic for the hypothesis H0 : µ = 2 vs. HA : µ ≠ 2. (b) [5points] Whatisthe(approximate) criticalt value that we should compare this statistic to if we want to use a 90% confidence? For 95% confidence? For 99% confidence? Do you reject the null hypothesis at any ofthese levels?What educated guess can youmake aboutthe p-value of this test?
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