Question

A company claims that its detergent 'KleenGlo' keeps your surfaces clean for an average of 18...

A company claims that its detergent 'KleenGlo' keeps your surfaces clean for an average of 18 hours, and you do not believe that it lasts this long. You want to perform a test of significance on the mean with a significance of 0.05, so you buy 18 bottles of KleenGlo and find that the mean number of hours those bottles keep a surface clean for is 15 hours with a standard deviation of 5 hours.  

What is the value of your test statistic ?t (as given by the formula)? Round your answer to 2 decimal places.

Math   Statistics-And-Probability   
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Answer #1

Solution:

This a right (One) tailed test.

The null and alternative hypothesis is,  

Ho: 18

Ha: 18

The test statistics,

t =( - )/ (s /n)

= ( 15 - 18 ) / ( 5 / 18 )

= -2.55

P-value = 0.0104

The p-value is p = 0.0104 < 0.05, it is concluded that the null hypothesis is rejected.

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