A random sample of 89 observations produced a mean x (x bar) = 25.8 and a standard deviation s= 2.4. - find a 95, 90, and 99% confidence interval for u. In a sample of 304,000 items mailed between Dec. 10 and Mar. 3, the accounting firm determined that 268,100 items were delivered on time. Assuming a confidence level of 95%, the likelihood of an item being delivered on time is in the interval __ , __. The mean gas mileage for a hybrid car is 56 miles per gallon (MPG). Suppose that the gas mileage is approximately normally distributed with a standard deviation of 3.3 MPG. a. The probability that a randomly selected hybrid gets more than 62 MPG is __? b. The probability that a randomly selected hybrid gets 50 MPG or less is __? c. The probability that a randomly selected hybrid gets between 57 and 62 MPG is __? d. The probability that a randomly selected hybrid gets less than 46 MPG is __? The random sample shown below was selected from a normal distribution. 9, 3, 7, 3, 9, 5. a. construct a 95% confidence interval for the population mean u __ , __. b. assume that sample mean x (x bar) and sample standard deviation s remains exactly the same as those you just calculated but that are based on a sample of n=25 observations. Repeat part a. what is the effect of increasing the sample size on the width of the confidence intervals? The confidence interval is __ , __? What is the effect of the sample size on the width of the confidence interval? As the sample size increases, the width increases, stays same or decreases