Question

A consumer organization wants to estimate the actual treadwear index of a brand name of tires...

A consumer organization wants to estimate the actual treadwear index of a brand name of tires that claims “graded 150” on the sidewall of the tire. A random sample of n=15 indicate a sample mean treadwear index of 141.8 and a sample standard deviation of 19.3.

a. Assuming that the population of treadwear indexes is normally distributed, construct a 90% confidence interval estimate of the population mean treadwear index for tires produced by this manufacturer under this brand name. (Round two decimal places

b. Do you think that the consumer organization should accuse the manufacturer of producing tires that do not need the performance information on the sidewall of the tire?

c. Explain why and observe treadwear index of 206 for particular tire is not an usual, even though it is outside of the confidence interval developed in (a)

Homework Answers

Answer #1

A random sample of n=15 indicate a sample mean treadwear index of xbar =141.8 and a sample standard deviation of s= 19.3.

90% confidence interval of population mean

Xbar +/- [ tcritical * ( s / sqrt ( n ) ) ]

141.8 +/- [ 1.7613 * ( 19.3 / sqrt ( 15 ) ) ]

133.02 < mu < 150.58

No, there is no grounds to allegate wrong-doing because the 90% confidence interval contains 150, which means that the sample mean is not statistically significantly different from the claimed tread wear index.

Comparing means by z and t distributions is an endeavor to compute probabilities; these methods cannot be legitimately used to determine whether a single observation is within or outside of expected limits.

Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
A consumer organization wants to estimate the actual tread wear index of a brand name of...
A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims​ "graded 150​" on the sidewall of the tire. A random sample of n=21 indicates a sample mean tread wear index of 137.3 and a sample standard deviation of 24.3. a.a. Assuming that the population of tread wear indexes is normally​ distributed, construct a 90% confidence interval estimate of the population mean tread wear index for tires produced by this manufacturer under...
A consumer organization wants to estimate the actual tread wear index of a brand name of...
A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims​ "graded 200​" on the sidewall of the tire. A random sample of n=20 indicates a sample mean tread wear index of 196.6. and a sample standard deviation of 29.7. Complete parts​ (a) . Assuming that the population of tread wear indexes is normally​ distributed, construct a 95% confidence interval estimate of the population mean tread wear index for tires produced by...
A consumer organization wants to estimate the actual tread wear index of a brand name of...
A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims​ "graded 200 on the sidewall of the tire. A random sample ofn equals 18indicates a sample mean tread wear index of192.5 and a sample standard deviation of22.7 Complete parts​ (a) through​ (c). a.a. Assuming that the population of tread wear indexes is normally​ distributed, construct a90 % confidence interval estimate of the population mean tread wear index for tires produced by...
A consumer organization wants to estimate the actual tread wear index of a brand name of...
A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims​ "graded 250​" on the sidewall of the tire. A random sample of n equals n=25 indicates a sample mean tread wear index of 237.3 and a sample standard deviation of 27.6 Complete parts​ (a) through​ (c). a. Assuming that the population of tread wear indexes is normally​ distributed, construct a 99 % confidence interval estimate of the population mean tread wear...
A consumer organization wants to estimate the actual tread wear index of a brand name of...
A consumer organization wants to estimate the actual tread wear index of a brand name of tires that claims​ "graded 250​" on the sidewall of the tire. A random sample of n equals 15 indicates a sample mean tread wear index of 242.9 and a sample standard deviation of 18.3. Complete parts​ (a) through​ (c). A. Assuming that the population of tread wear indexes is normally​ distributed, construct a 95 % confidence interval estimate of the population mean tread wear...
A researcher is interested in evaluating a certain brand of radial auto tire. Twenty tires are...
A researcher is interested in evaluating a certain brand of radial auto tire. Twenty tires are randomly selected from retail outlets throughout the country, and each is placed on a special machine which rotates the tires at a constant speed (equivalent to 55 miles per hour) against the friction equivalent of a 4000 pound auto being driven on a smooth highway. Each tire is run until there is no tread left. The number of miles (in thousands) were as follows:...
(1) Let µ be the mileage of a certain brand of tire. A sample of n...
(1) Let µ be the mileage of a certain brand of tire. A sample of n = 22 tires is taken at random, resulting in the sample mean x = 29, 132 and sample variance s2= 2, 236. Assuming that the distribution is normal, find a 99 percent confidence interval for µ. (2)We need to estimate the average of a normal population and from measurements on similar populations we estimate that the sample mean is s2 = 9. Find the...
The manager of a paint supply store wants to estimate the actual amount of paint contained...
The manager of a paint supply store wants to estimate the actual amount of paint contained in 1​-gallon cans purchased from a nationally known manufacturer. The​ manufacturer's specifications state that the standard deviation of the amount of paint is equal to 0.01 gallon. A random sample of 50 cans is​ selected, and the sample mean amount of paint per 1​-gallon can is 0.996 gallon. Complete parts​ (a) through​ (d). a. Construct a 95​% confidence interval estimate for the population mean...
The manager of a gasoline supply corporation wants to estimate the actual amount of gasoline contained...
The manager of a gasoline supply corporation wants to estimate the actual amount of gasoline contained in standard 42-gallon barrels purchased from a nationally known manufacturer. The manufacturer’s specifications state that the amount of gasoline is normally distributed with a standard deviation of 0.65 gallon. A random sample of 25 barrels is selected, and the sample mean amount of gasoline per 42-gallon barrel is 42.15 gallons. Construct a 90% confidence interval estimate for the population mean amount of gasoline contained...
The manager of a gasoline supply corporation wants to estimate the actual amount of gasoline contained...
The manager of a gasoline supply corporation wants to estimate the actual amount of gasoline contained in standard 42-gallon barrels purchased from a nationally known manufacturer. The manufacturer’s specifications state that the amount of gasoline is normally distributed with a standard deviation of 0.65 gallon. A random sample of 25 barrels is selected, and the sample mean amount of gasoline per 42-gallon barrel is 42.15 gallons. Construct a 90% confidence interval estimate for the population mean amount of gasoline contained...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT