Question

The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...

The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 8800 observations, the sample mean interval was x1 = 61.2 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 24,404 observations, the sample mean time interval was x2 = 71.2 minutes. Historical data suggest that σ1 = 8.49minutes and σ2 = 12.62 minutes. Let μ1 be the population mean of x1 and let μ2 be the population mean of x2.

(a) Compute a 95% confidence interval for μ1μ2. (Use 2 decimal places.)

lower limit    
upper limit    

(b) Comment on the meaning of the confidence interval in the context of this problem. Does the interval consist of positive numbers only? negative numbers only? a mix of positive and negative numbers? Does it appear (at the 95% confidence level) that a change in the interval length between eruptions has occurred? Many geologic experts believe that the distribution of eruption times of Old Faithful changed after the major earthquake that occurred in 1959.

Because the interval contains only positive numbers, we can say that the interval length between eruptions has gotten shorter.Because the interval contains both positive and negative numbers, we can not say that the interval length between eruptions has gotten longer.     We can not make any conclusions using this confidence interval.Because the interval contains only negative numbers, we can say that the interval length between eruptions has gotten longer.

Homework Answers

Answer #1

Solution :

For sample 1 :x̅1 = 61.2, σ1 = 8.49, n1 = 8800

For sample 2 :x̅2 = 71.2, σ2 = 12.62, n2 = 24404

(a) 95% Confidence interval :  

At α = 0.05, two tailed critical value, z_c = ABS(NORM.S.INV(0.05/2)) = 1.96

Lower Bound = (x̅1 - x̅2) - z_c*√(σ1²/n1 +σ2²/n2)

= (61.2 - 71.2) - 1.96*√(8.49²/8800 + 12.62²/24404) =-10.24

Upper Bound = (x̅1 - x̅2) + z_c*√(σ1²/n1 +σ2²/n2)

= (61.2 - 71.2) + 1.96*√(8.49²/8800 + 12.62²/24404) =-9.76

(b) Because the interval contains only negative numbers, we can say that the interval length between eruptions has gotten longer.

Please like if it helps me please please

Thank you so much

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
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9200 observations, the sample mean interval was x1 = 63.8 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 24,872...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9460 observations, the sample mean interval was x1 = 62.6 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 23,000...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9760 observations, the sample mean interval was x1 = 62.6 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 23,468...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9120 observations, the sample mean interval was x1 = 62.0 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 25,106...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9800 observations, the sample mean interval was x1 = 64.4 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 24,404...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870...
The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9160 observations, the sample mean interval was x1 = 61.8 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 23,351...
In a sample of 500 eruptions of the Old Faithful geyser at Yellowstone National Park, the...
In a sample of 500 eruptions of the Old Faithful geyser at Yellowstone National Park, the mean duration of the eruptions was 3.32 minutes and the standard deviation was 2.09 minutes. A random sample of size 30 is drawn from this population. a. Describe the sampling distribution of the eruptions of the Old Faithful geyser. b. What is the probability that the mean duration of eruptions is between 2.5 minutes and 4 minutes?
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy)...
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy) was performed. Let x1 be a random variable that represents the score of a mother on an empathy test (as regards her baby). Let x2 be the empathy score of a father. A random sample of 31 mothers gave a sample mean of x1 = 69.55. Another random sample of 36 fathers gave x2 = 59.00. Assume that σ1 = 10.71 and σ2 =...
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy)...
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy) was performed. Let x1 be a random variable that represents the score of a mother on an empathy test (as regards her baby). Let x2be the empathy score of a father. A random sample of 37 mothers gave a sample mean of x1 = 67.00. Another random sample of 27 fathers gave x2 = 61.04. Assume that σ1 = 10.92 and σ2 = 11.62....
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy)...
A study of parental empathy for sensitivity cues and baby temperament (higher scores mean more empathy) was performed. Let x1 be a random variable that represents the score of a mother on an empathy test (as regards her baby). Let x2 be the empathy score of a father. A random sample of 29 mothers gave a sample mean of x1 = 67.68. Another random sample of 34 fathers gave x2 = 60.36. Assume that σ1 = 10.85 and σ2 =...
ADVERTISEMENT
Need Online Homework Help?

Get Answers For Free
Most questions answered within 1 hours.

Ask a Question
ADVERTISEMENT