A variable is normally distributed with mean 18 and standard deviation 4. Use your graphing calculator to find each of the following areas. Write your answers in decimal form. Round to the nearest thousandth as needed. a) Find the area to the left of 17. b) Find the area to the left of 12. c) Find the area to the right of 16. d) Find the area to the right of 24. e) Find the area between 12 and 25.

Data on oxide thickness of semiconductors are as follows: 426 432 418 418 421 436 418 408 431 435 423 426 411 434 435 432 411 426 407 439 422 426 412 416 consider this data as a sample of the population. (a) calculate a point estimate of the mean oxide thickness for all wafers in the population. (round your answer to 3 decimal places.) (b) calculate a point estimate of the standard deviation of oxide thickness for all wafers in the population. (round your answer to 2 decimal places.) (c) calculate the standard error of the point estimate from part (a). (round your answer to 2 decimal places.) (d) calculate a point estimate of the median oxide thickness for all wafers in the population. (express your answer to 1 decimal places.) (e) calculate a point estimate of the proportion of wafers in the population that have oxide thickness greater than 430 angstrom. (round your answer to 4 decimal places.)