Approximate the variance of times and approximate the standard deviation of the times,

A standardized​ exam's scores are normally distributed. In a recent​ year, the mean test score was 1544 and the standard deviation was 314.The test scores of four students selected at random are 1940​, 1290​, 2250​,and 1420.Find the​ z-scores that correspond to each value and determine whether any of the values are unusual. ​(Round to 2 decimal places as​ needed.)

Jeremiah earned a score of 530 on Exam A that had a mean of 450 and a standard deviation of 40. He is about to take Exam B that has a mean of 63 and a standard deviation of 20. How well must Jeremiah score on Exam B in order to do equivalently well as he did on Exam A? Assume that scores on each exam are normally distributed.

Round each z-score to the nearest hundredth. A data set has a mean of  x = 214  and a standard deviation of 44. Find the z-score for each of the following. (a) x = 200   (b) x = 224   (c) x = 300   (d) x = 100

Assume that the mean height of men in the United States is 70 inches, with a standard deviation of 3 inches.  A particular man is 80 inches tall.  Find the z-score of his height.  (Round to two decimal places.)

A manufacturer of light bulbs finds that one light bulb model has a mean life span of 1025 h with a standard deviation of 83 h.Find the z-scores for lightbulbs which last 850 and 900 h. (Round your answers to two decimal places.) 850 h: z = 900 h: z =