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Have you ever been frustrated because you could not get a container of some sort to release the last bit of its contents? The article 鈥淪hake, Rattle, and Squeeze: How Much Is Left in That Container?鈥 (Consumer Reports, May 2009: 8) reported on an investigation of this issue for various consumer products. Suppose five \(6.0oz\) tubes of toothpaste of a particular brand are randomly selected and squeezed until no more toothpaste will come out. Then each tube is cut open and the amount remaining is weighed, resulting in the following data (consistent with what the cited article reported):

\(.53,.65,.46,.50,.37.\)

Does it appear that the true average amount left is less than \(10\% \) of the advertised net contents?

a. Check the validity of any assumptions necessary for testing the appropriate hypotheses.

b. Carry out a test of the appropriate hypotheses using a significance level of \(.05\). Would your conclusion change if a significance level of \(.01\) had been used?

c. Describe in context type I and II errors, and say which error might have been made in reaching a conclusion.

Short Answer

Expert verified

(a) Assumptions are met.

(b) The true average amount left is less than\(10\% \)of\(0.6oz\), that corresponds with\(0.6oz\) is supported by appropriate evidence at significance level\(0.05\). The true average amount left is less than\(10\% \)of\(0.6oz\), that corresponds with\(0.6oz\) is not supported by appropriate evidence at significance level\(0.01\).

(c) The context for type I and type II is: The true average quantity remaining is at least \(10\% \) of the reported net contents, which is incorrect.

Step by step solution

01

Define p-value in hypothesis testing.

The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis states the opposite of the null hypothesis.

\(\begin{array}{l}{H_0}:\mu = 0\\{H_a}:\mu \ne 0\end{array}\)

The formula for the value of the test statistic is given by, \(t = \frac{{\bar x - {\mu _0}}}{{s/\sqrt n }}\).

02

Assumption for test the appropriate hypothesis.

(a)

NORMAL PROBABILITY PLOT:

The horizontal axis shows the data values, while the vertical axis shows the standardised normal scores.

The standardised normal scores are the z-scores in the normal probability table in the appendix corresponding to an area of \(\frac{{j - 0.5}}{n}\) (or the closest area) with \(j \in \{ 1,2,3,...,n\} \) if the data comprises n data values. The least standardised score correlates to the smallest data value, and so on.

The population distribution is essentially normal if the pattern in the normal probability plot is roughly linear and does not contain strong curvature.

The population distribution is about normal, and known that the conditions for testing the necessary hypotheses are met because the normal probability plot does not have severe curvature and is essentially linear.

03

Test the appropriate hypothesis.

(b)

The mean is the ration of sum of all values and the total number of values.

\(\begin{aligned}{c}\bar x &= \frac{{0.53 + 0.65 + 0.46 + 0.50 + 0.37}}{5}\\ &= \frac{{2.51}}{5}\\ &\approx 0.502\end{aligned}\)

The square of the variance is the standard deviation.

\(\begin{aligned}{c}s &= \sqrt {\frac{{{{(0.53 - 0.502)}^2} + \ldots . + {{(0.37 - 0.502)}^2}}}{{5 - 1}}} \\ &\approx 0.1023\end{aligned}\)

Let the given be:

\(\begin{array}{l}n = 5\\\alpha = 0.05/0.01\end{array}\)

Claim that the true average amount left is less than\(10\% \)of\(0.6oz\), that corresponds with\(0.6oz\).

The value of the test statistic:

\(\begin{aligned}{c}t &= \frac{{\bar x - {\mu _0}}}{{s/\sqrt n }}\\ &= \frac{{0.502 - 0.6}}{{0.1023/\sqrt 5 }}\\ &\approx - 2.142\end{aligned}\)

The P-value is the chance of getting the test statistic's result, or a number that is more severe. The P-value is the number (or interval) in the column header of the T table in the appendix that contains the t-value in the row\(\begin{array}{c}df = n - 1\\ = 5 - 1\\ = 4\end{array}\)for the student.

\(0.025 < P < 0.05\)

As the P-value is smaller than the significance level, so the null hypothesis is rejected.

\(\begin{array}{l}P < 0.05 \Rightarrow Reject {H_0}\\P > 0.01 \Rightarrow Fail to Reject {H_0}\end{array}\)

The true average amount left is less than \(10\% \) of \(0.6oz\), that corresponds with \(0.6oz\) is supported by appropriate evidence at significance level \(0.05\). The true average amount left is less than \(10\% \) of \(0.6oz\), that corresponds with \(0.6oz\) is not supported by appropriate evidence at significance level \(0.01\).

04

Describe the Type I and Type II error.

(c)

Let the given be:

\(\begin{array}{l}n = 5\\\alpha = 0.05/0.01\end{array}\)

Claim that the true average amount left is less than\(10\% \)of\(0.6oz\), that corresponds with\(0.6oz\).

The null hypothesis states that the population mean is equal to the value mentioned in the claim. If the null hypothesis is the claim, then the alternative hypothesis states the opposite of the null hypothesis.

\(\begin{array}{l}{H_0}:\mu = 0.6\\{H_a}:\mu < 0.6\end{array}\)

Type I error: When\({H_0}\)is true, reject the null hypothesis\({H_0}\).

Interpretation: The true average amount remaining is less than\(10\% \)of the advertised net contents, which is incorrect.

Type Il error: When\({H_0}\)is false, fail to reject the null hypothesis\({H_0}\).

Interpretation: The true average quantity remaining is at least \(10\% \) of the reported net contents, which is incorrect.

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Most popular questions from this chapter

Before agreeing to purchase a large order of polyethylene sheaths for a particular type of high-pressure oil filled submarine power cable, a company wants to see conclusive evidence that the true standard deviation of

sheath thickness is less than .05 mm. What hypotheses should be tested, and why? In this context, what are the type I and type II errors?

The calibration of a scale is to be checked by weighing a 10-kg test specimen 25 times. Suppose that the results of different weightings are independent of one another and that the weight on each trial is normally distributed with 蟽 = .200 kg. Let 碌 denote the true average weight reading

on the scale.

a.What hypotheses should be tested?

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c.For a test with 伪 =.01, what is the probability that recalibration is judged unnecessary when in fact 碌=10.1? When 碌= 9.8?

A mixture of pulverized fuel ash and Portland cement to be used for grouting should have a compressive strength of more than 1300 KN/m2 . The mixture will not be used unless experimental evidence indicates conclusively that the strength specification has been met. Suppose compressive strength for specimens of this mixture is normally distributed with 蟽= 60. Let 碌 denote the true average compressive strength.

a.What are the appropriate null and alternative hypotheses?

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In Problems \(19\) and \(20\) verify that the indicated expression is an implicit solution of the given first-order differential equation. Find atleast one explicit solution \(y = \phi (x)\) in each case. Use a graphing utility to obtain the graph of an explicit solution. Give an interval \(I\) of definition of each solution \(\phi \).

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