e Calculate a point estimate of the proportion of wafers in

(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 four decimal places.)

Solution

arrange in increasing order:
408   410   410   412   413   415   417   418   420   421   422   423   425   426   426   426   428   429   431   433   433   434   434   435

n = 24

a.
mean = (408+410+...+435)/24
= 422.875

b.
standard deviation = sqrt(((408-422.875)^2 + ... + (435-422.875)^2) / (24-1))
= 8.51

c.
standard error = 8.507/ sqrt(24)
= 1.74

d.
median is the average of middle 2 observations in the sorted data
= (423+425)/2
= 424.0

e.
there are 6 observations more than 430
so proportion = 6/24
= 0.2500