We calculated the 99% conﬁdence interval for the average age of runners in the 2014 London Marathon as (263.5237, 283.472) based on a sample of 100 runners. How could we decrease the width of this interval without losing conﬁdence?
We calculated the 99% conﬁdence interval for the average age of runners in the 2014 London...
3. Age of runners. The average of the runners’ ages is µ = 34.05 years with a standard deviation of σ = 9.83. A simple random sample of 100 runners is taken. a. Find the standard deviation of the sample mean, σx. b. In your opinion, would you be surprised to get a sample (of size 100) with an average age of 36 years? Why or why not? (One idea: start by calculated this probability, the probability of getting an...
(1 point) Suppose we want a 99% confidence interval for the average amount spent on books by freshmen in their first year at college. The amount spent has a normal distribution with standard deviation $30. How large should the sample be if the margin of error is to be less than $4? ANSWER:
Question 7 (1 point) The owner of a local golf course wants to determine the average age of the golfers that play on the course in relation to the average age in the area. According to the most recent census, the town has an average age of 55.89. In a random sample of 30 golfers that visited his course, the sample mean was 45.84 and the standard deviation was 6.514. Using this information, the owner calculated the confidence interval of...
Assume we have taken an SRS of 49 UCLA students and calculated a 95% confidence interval for the mean age to be 23 < µ< 27 years. Determine which of the following interpretations are True. Then answer parts i and ii in the space below. A. A 95% confidence interval for the mean age of students at UCLA is 23 to 27. This means that 95% of all students are in this interval. B. A 95% confidence interval for the mean...
aminate sheets under specified conditions was calculated as 5.81 695 A 95% CI for true average mount of war age mm o warpage is normally distributed. ased on a sample size and the as surm on that amount r n (a) Suppose you want to test H0: μ-7 versus Ha: μ 7 using α = 0.05. what conclusion would be appropriate, and why? since the null value o 7 is in the 95% confidence interval we re ect 0 There...
Does 10K running time decrease when the runner listens to music? Nine runners were timed as they ran a 10K with and without listening to music. The running times in minutes are shown below. Running Time With Music 42 47 35 50 42 49 49 47 46 Without 46 45 38 51 43 53 51 45 48 Music Assume a Normal distribution. What can be concluded at the the a = 0.01 level of significance? For this study, we should...
We want to know the average number of hours financial advisors in your area work a month. You survey 76 random advisors and find the average hours they work per month is 189. You also believe that the population standard deviation is 20 hours a month. Give a 99% confidence interval for the estimated average number of hours financial advisors work per month. Confidence Interval Estimate for the Mean Data Population Standard Deviation 20 Sample Mean 189 Sample Size 76...
We would like to estimate the true average age of customers for a particular company. How large would the sample size need to be for the margin of error (based on 95% confidence) to be 1 year? Suppose that, based on previous research, we can assume the standard deviation of customer ages will be 14. Select one: a. 3872 b. 784 C. 753 X d. 659
A chemical company has two factories, one in London and the other in Windsor. We wish to determine if there is any difference between the two factories with respect to how much methane is being put into the air. Readings of methane expulsion are taken at randomly spaced intervals in the two cities. The 8 readings in London show an average of 0.23 parts per million (ppm) with a standard deviation of 0.07 ppm. The 11 readings in Windsor show...
A survey of 25 randomly selected customers found that their average age was 31.84 years with a standard deviation of 9.84 years. What would the critical value t* be for a 95% confidence interval with 99 degrees of freedom? What would the margin of error be for a 95% confidence interval for this data (with the sample size of 25)? Construct a 95% confidence interval for the mean age of all customers for this data (with the sample size of...