STAISTIC HELP! its driving me crazy! >:(

[Rozalin]

Q6) The weights of bags of popcorn are normally distributed with mean of 200 g and 60% of all bags weighing between 190 g and 2009.

A) Write down the median of the weight of the bags of popcorn. its 200g

I NEED HELP WITH THE FOLLOWING PART
b) Find the standard deviation of the weights of the bags of popcorn

show ur working 
thanks! 

I've attached the question paper, its from January 2008 S1 edexcel

[Rozalin]

=__=

[astarmathsandphysics]

should be 210g
P(200<w<210)=0.3 so P(w<210)=0.5+0.3
z corresponding to probability of 0.8 is 0.84
z=(x-u)/s
0.84=(210-200)/s=10/s
s=10/0.84=11.76

[Rozalin]

should be 210g
P(200<w<210)=0.3 so P(w<210)=0.5+0.3
z corresponding to probability of 0.8 is 0.84
z=(x-u)/s
0.84=(210-200)/s=10/s
s=10/0.84=11.76

Thankssssssss alooooooooooooot :DDD

but I have a question :$

P(200<w<210)=0.3

From where did you get the 0.3? and the 0.5?

[Rozalin]

and how did u get 0.84 @_@?

[astarmathsandphysics]

go to you normal tables.
The prob is 0.8 and all the probs are in the body of you tables. The closest number to 0.8 in the tables is 0.7995. This correxponds to 0.8 on the lest and 0.04 above ie 0.84

[Rozalin]

thankssssss

[astarmathsandphysics]

look at this

[Rozalin]

OMG THANK YOU! I found it really helpful! you made my dayyyy sirrrr