Question

1. To test a hypothesis that package size has no effects on sales, a researcher collects the sales data of five different packages of one particular brand. A two sample pooled-variance t test should be recommended to compare the mean sales among the 5 different packages.

True

False

2. For air travelers, one of the biggest complaints is of the waiting time between when the airplane taxis away from the terminal until the flight takes off. This waiting time is known to have a positively skewed distribution with a mean of 10 minutes and a standard deviation of 8 minutes. Suppose 100 flights have been randomly sampled. Describe the sampling distribution of the mean waiting time between when the airplane taxis way from the terminal until the flight takes off for these 100 flights.

Distribution is approximately normal with mean = 10 minutes and standard error = 8 minutes.

Distribution has a long tail on the right with mean = 10 minutes and standard error = 8 minutes.

Distribution has a long tail on the right with mean = 10 minutes and standard error = 0.8 minutes.

Distribution is approximately normal with mean = 10 minutes and standard error = 0.8 minutes.

3. What is the relationship between a 95 confidence interval and a 99 confidence interval from the same sample?

They are of the same width.

Needs more information to judge.

The 99% interval will be wider.

The 95% interval will be wider.

4. Records show that the amount of gasoline purchased per car at a large service station has a population mean of 15 gallons and a population standard deviation of 5 gallons. If a random of 40 cars is selected, the chance that the sample mean will be between 13.5 and 16.5 gallons is ____?

> 95%

between 80% and 85%

<80%

between 90% and 95%

between 85% and 90%

PLEASE ANSWER ALL THE FOLLOWING. NO WORK NEEDS TO BE SHOWN.

Answer 1

Solution:-

1) False, Anova test should be used for comparison.

2)

Distribution is approximately normal with mean = 10 minutes and standard error = 0.8 minutes.

3) The 99% interval will be wider.

The confidence coefficient for 99% confidence interval is greater than confidence coefficient for 95% confidence interval.

4) If a random of 40 cars is selected, the chance that the sample mean will be between 13.5 and 16.5 gallons is between 90% and 95%.

Mean = 15, S.D = 5

x₁ = 13.5

x₂ = 16.5

By applying normal distribution:-

z₁ = - 1.897

z₂ = 1.897

P( - 1.897 < z < 1.897) = P(z > - 1.897) - P(z > 1.897)

P( - 1.897 < z < 1.897) = 0.9711 - 0.0289

P( - 1.897 < z < 1.897) = 0.9422