A particular brand of tires claims that its deluxe tire averages at least 50,000 miles before it needs to be replaced. From past studies of this tire, the standard deviation is known to be 8,000. A survey of owners of that tire design is conducted. Of the 30 tires surveyed, the mean lifespan was 46,300 miles with a standard deviation of 9,800 miles. Using alpha = 0.05, is the data highly consistent with the claim? Note: If you are using a Student's t-distribution for the problem, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.) Part (a) Part (b) Part (c) Part (d) State the distribution to use for the test. (Round your answers to two decimal places.) X ~ , Part (e) What is the test statistic? (If using the z distribution round your answers to two decimal places, and if using the t distribution round your answers to three decimal places.) = Part (f) What is the p-value? (Round your answer to four decimal places.) Explain what the p-value means for this problem. If H0 is true, then there is a chance equal to the p-value that the average life span of a tire is 46,300 miles or less.If H0 is true, then there is a chance equal to the p-value that the average life span of a tire is not 46,300 miles or less. If H0 is false, then there is a chance equal to the p-value that the average life span of a tire is not 46,300 miles or less.If H0 is false, then there is a chance equal to the p-value that the average life span of a tire is 46,300 miles or less. Correct! A p-value is the probability that an outcome of the data will happen purely by chance when H0 is true. Part (g) Part (h) Indicate the correct decision ("reject" or "do not reject" the null hypothesis), the reason for it, and write an appropriate conclusion. (i) Alpha (Enter an exact number as an integer, fraction, or decimal.) ? = (ii) Decision: reject the null hypothesisdo not reject the null hypothesis (iii) Reason for decision: Since ? < p-value, we do not reject the null hypothesis.Since ? > p-value, we do not reject the null hypothesis. Since ? < p-value, we reject the null hypothesis.Since ? > p-value, we reject the null hypothesis. (iv) Conclusion: There is sufficient evidence to conclude that the average life span of the tires is less than 50,000.There is not sufficient evidence to conclude that the average life span of the tires is less than 50,000.
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
Note: If you are using a Student's t-distribution for the problem, you may assume that the underlying population is
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Part (a)
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Part (b)
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Part (c)
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Part (d)
State the distribution to use for the test. (Round your answers to two decimal places.)
X~ -
Part (e)
What is the test statistic? (If using the z distribution round your answers to two decimal places, and if using the t distribution round your answers to three decimal places.)
= -
Part (f)
What is the p-value? (Round your answer to four decimal places.)
Explain what the p-value means for this problem.IfH0is true, then there is a chance equal to the p-value that the average life span of a tire is 46,300 miles or less.IfH0is true, then there is a chance equal to the p-value that the average life span of a tire is not 46,300 miles or less. IfH0is false, then there is a chance equal to the p-value that the average life span of a tire is not 46,300 miles or less.IfH0is false, then there is a chance equal to the p-value that the average life span of a tire is 46,300 miles or less.H0is true. -
Part (g)
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Part (h)
Indicate the correct decision ("reject" or "do not reject" the null hypothesis), the reason for it, and write an appropriate conclusion.(i) Alpha (Enter an exact number as an integer, fraction, or decimal.)
? =
(ii) Decision:reject the null hypothesisdo not reject the null hypothesis
(iii) Reason for decision:Since ? < p-value, we do not reject the null hypothesis.Since ? > p-value, we do not reject the null hypothesis. Since ? < p-value, we reject the null hypothesis.Since ? > p-value, we reject the null hypothesis.
(iv) Conclusion:There is sufficient evidence to conclude that the average life span of the tires is less than 50,000.There is not sufficient evidence to conclude that the average life span of the tires is less than 50,000. -
Part (i)
Construct a 95% confidence interval for the true mean. Sketch the graph of the situation. Label the point estimate and the lower and upper bounds of the confidence interval. (Round your lower and upper bounds to the nearest whole number.)
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