1. How long does it take an ambulance to respond to a requestfor emergency medical aid? One of the goals of one study was toestimate the response time of ambulances using warning lights (Ho& Lindquist, 2001). They timed a total of 67 runs in a smallrural county in Minnesota. They calculated the mean response timeto be 8.51 minutes, with a standard deviation of 6.64 minutes.Calculate a 95% confidence interval for the mean for this set ofdata.

1. State the desired level of confidence.
2. Calculate the confidence interval and confidence limits.
   • (1) Calculate the standard error of the mean(s¯¯¯X).(sX¯).
   • (2) Calculate the degrees of freedom (df?) andidentify the critical value of t.
   • (3) Calculate the confidence interval and confidencelimits.
3. Draw a conclusion about the confidence interval.

a 95% confidence interval was constructed for N = 67ambulance runs. Assuming the mean and standard deviation remainedthe same (¯¯¯X=8.51,s=6.64)…(X¯=8.51,s=6.64)…

1. What is the confidence interval for the mean for N =125 ambulance runs rather than 67?
2. What is the confidence interval for the mean for N =33 ambulance runs rather than 67?
3. How do these two confidence intervals compare with the 95%confidence interval of (6.89, 10.13) calculated in Exercise 8?

2. For each of the following situations, calculate a 95%confidence interval for the mean (? known), beginning with thestep, “Identify the critical value of z.”

1. ¯¯¯X=50.00,?¯¯¯X=3.00