Question

question 4
1 pts
ch 20 a tire manufacturer claims that one particular type of tire will last at least 50,000
miles. a group of angry customers does not believe this is so. they took a sample of 14 tires
to test if the mean mileage of the tires is really less than 50,000. if 0.0100 < p - value <
0.0200, what decision should be made if testing at the alpha = 0.05 level?
do not reject ho and conclude that the tires were not performing as claimed.
reject ho and conclude that the mean tire life really is 50,000 miles.
reject ho and conclude that the tires were not performing as claimed.
do not reject ho and conclude that the mean tire life really is 50,000 miles.
question 5
1 pts
ch 20 a veterinarian collects data on the number of times race horses are raced during
their career. the researcher finds the average number of races a horse enters is x - bar = 15.3
with a standard deviation of s = 6.8 in a sample of n = 20 horses.
the researcher notices one horse that has raced 45 times. this outlier poses a problem. what
should the researcher do?
increase the confidence level.
choose a z - interval instead of a t - interval since a z - interval is not affected by outliers.
\pwc\ results are not accurate.
drop the outlier and recalculate sample mean and standard deviation then proceed with a t - interval.

Explanation:

Question 4

In hypothesis testing, the decision rule is: if \(P - value<\alpha\), we reject the null hypothesis \(H_0\). Here, \(\alpha = 0.05\) and \(0.0100

Outliers can have a significant impact on the mean and standard deviation (which are used in \(t\) - intervals). Increasing the confidence level does not address the outlier issue. \(z\) - intervals assume known population parameters (not just sample data) and are not a solution for dealing with outliers in sample data. "PWC" is not a relevant concept here. The appropriate action is to drop the outlier (since it is an extreme value that may skew the results), recalculate the sample mean and standard deviation (which are sensitive to outliers), and then proceed with a \(t\) - interval (which is appropriate for small sample sizes (\(n = 20\)) when the population standard deviation is unknown).

Answer:

Reject \(H_0\) and conclude that the tires were not performing as claimed.

Question 5