A box of tickets has an average of 100, and an SD of 20. Four hundred draws will be made at random with replacement from this box.
(a) Estimate the chance that the average of the draws will be in the range 80 to 120.
(b). Estimate the chance that the average of the draws will be in the range 99 to 101.
2006-12-06 17:13:04 · 2 answers · asked by nothingconstant 7 in Science & Mathematics ➔ Mathematics
okay, now what.
2006-12-06 17:20:57 · answer #1 · answered by R-Diz 4 · 0⤊ 0⤋
you want to do a z-test:
SE = 20 / (sqrt(400)) = 20/20 = 1
for part 1, you are looking at (80-100)/1 = -20 and (120-100)/1 = 20. so look up what % of data lies outside of z values of -20 to 20? (I'd say about 0.)
for part 2, similarly, z = (99-100)/1 = -1, z = (101-100)/1 = 1, so what percentage of data lies outside of z=-1 to z=1? 31.73% if i remember correctly.
2006-12-06 17:32:34 · answer #2 · answered by Nick C 4 · 1⤊ 0⤋