Question 5 (1 mark) Attempt 2 The drying time of a certain type of paint under s

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Question 5 (1 mark) Attempt 2 The drying time of a certain type of paint under specified test conditions is known to be normally distributed with mean value 79 min and standard deviation 9.2 min. Chemists have proposed a new additive designed to decrease average drying time. It is believed that drying times with this additive will remain normally distributed with standard deviation 9.2 min. Because of the expense associated with the additive, evidence should strongly suggest an improvement in average drying time before such a conclusion is adopted. Let H be the true average drying time when the additive is used. The hypothesis are to be tested using a random sample of 33 observations. The rejection region is: 79-c Find the minimum value of c that yields a test with significance 0.01? 1.282 1.645 1.960 2.326 2.576 3.090 a(tail area) 0.1 0.05 0.025 0.01 0.005 0.001 %ile 90 95 97.5 99 99.5 99.9 Your answer can be rounded to four decimal digit accuracy when entered. C-Skipped

Explanation / Answer

Ans:

Significance level=0.01

cut off z value(left tailed)=normsinv(0.01)=-2.326

The rejection region is:

x-bar<=79-c

where,

c=2.326*9.2/sqrt(33)

c=3.7251

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