Question 3

Use the confidence level and the data from the example to find a confidence interval for the population estimate mu. Round your answer to the same number of decimal places as the sample mean. A random sample of 105 light bulbs had a mean life of 441 hours with a standard deviation of 40 hours. Construct a 90% confidence interval for the mean life, mu, of all light bulbs of this type.

433 hr < mu <449 hr

435 hr < mu <447 hr

431 hr < mu <451 hr

432 hr < mu <450 hr

Question 7

If z is a standard normal variable, find the probability that z is less than 1.13

0.1292

0.8708

0.8485

0.8907

Question 9

Use the confidence level and sample data given to construct a confidence interval for the population proportion p. n = 110, x = 55; confidence 88%

0.425 < p < 0.575

0.421 < p < 0.579

0.422 < p < 0.578

0.426 < p < 0.574

Question 13

Suppose X has a normal distribution. Find the indicated probability. The mean is 15.2 and the standard deviation is 0.9. Find the probability that X is greater than 17.

0.9713

0.9821

0.0228

0.9772