Question

A farmer cuts hazel twigs to make into beam poles to sell at the market.He says that the sticks are each 240cm long but in fact the lengths of the stick are normally distrinuted such that 55% of the sticks are longer than 240cm and 10% are longer than 250cm.Find the probability that a randomly selected stick is shorter than 235cm.

Answer 1

so P(x<240) = .45 and P(x < 250)= .9
(240-m)/s = -.125 and (250-m)/s = 1.282 , using http://davidmlane.com/normal.html

m - .125s = 240 and m + 1.282s = 250

subtract them:
1.407s = 10
s = 7.107, then m = 240.888

use the above webpage again, let me know what you got

Answer 2

I got 0.203 which is the answer.

Answer 3

I got the same
Btw, do you still use tables in the back of textbooks for these type of questions?
How are these taught in class these days, I have been retired for 23 years, so I am curious what happened to the old ways.

Answer 4

Only to calculate z values of area, we use calculators.But there is table given at the back if one wants to use it.

Answer 5

I use calculator.There is table at the back now also and student are provided table in the examinations.Its quite easier to deal with calculator than tables.

Answer 6

To calculate area we use calculator but to get z score of area we use the tables at back.