Asked by May
The yearly rainfall in Vancouver, B.C. follows a normal distribution with standard deviation 172 mm. In 20% of years, the city gets over 1200 mm of rain. What is the mean annual rainfall in Vancouver (in mm)?
The answer is 1055.5 mm....not sure how to get this answer.
The answer is 1055.5 mm....not sure how to get this answer.
Answers
Answered by
Scott
a z-score table will give the number of s.d. above the mean for the 20% figure
the z-score is .84
so 1200 mm is .84 s.d. above the mean
1200 - (.84 * 172) = ?
the z-score is .84
so 1200 mm is .84 s.d. above the mean
1200 - (.84 * 172) = ?
Answered by
Emma
why is the z-score 0.84
Answered by
Lynn
took me way too long but i got it:
1 - .20 = .8000
*Did this because you are looking for P(x>1200) therefore, you are looking at for a right side probability, z table only give you left.
Find .8000 INSIDE z chart, the closest number is .7995 = .84
x - (z*std.dev) = 1200 - (.84*172) = 1055.5
1 - .20 = .8000
*Did this because you are looking for P(x>1200) therefore, you are looking at for a right side probability, z table only give you left.
Find .8000 INSIDE z chart, the closest number is .7995 = .84
x - (z*std.dev) = 1200 - (.84*172) = 1055.5