Adding random bars both with normal distribution

AWall

New member
Joined
Jan 15, 2017
Messages
3
Afternoon everyone

I have two probability questions I have had a go at, Can someone have a look and see if they are correct or where i'm gonig wrong.

Mean length 10cm s.d 4mm - Bar 1
Mean length 20cm sd 6mm - Bar 2

So probability of picking bar 1 & bar 2 at randomand the total length being greater than 30.8cm

so add mean[FONT=MathJax_Math-italic] =[/FONT] 30cm
s.d =1cm

(30.8-30)/1
=0.8

using z table = 0.2119

Also difference in length of two random bars from the same as above being less than 9.8,
so Minus then
mean=10cm
s.d = 0.2cm

(9.8-10)/0.2
=-1

using -z table i get = 0.1587


sorry not used correct symbols on phone and doesn't seem to want to work.

Can somebody check these are correct.

thanks

Andy
 

AWall

New member
Joined
Jan 15, 2017
Messages
3
bump please. I assume I've got things wrong so will need to get figure out what i need to do.

thanks

Andy
 

AWall

New member
Joined
Jan 15, 2017
Messages
3
Evening all

Can somebody please help.

thanks

Andy
 
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