If the random variable x is normally distributed with a mean equal to .45 and a standard deviation equal to .40, then P(x ≥ .75) is:

Question

amistre64 · Answer

z = (x-mean)/sd

amistre64 · Answer

z = (.75 - .45)/.40

amistre64 · Answer

the rest is gotten from a ztable or a calculator i believe; you got a ti83?

anonymous · Answer

I got a ti89 :)

anonymous · Answer

and the table too

amistre64 · Answer

press: 2nd, vars, normalCDF ( .75,9999,.45,.40 ) http://www.wolframalpha.com/input/?i=normalCDF+%28+.75%2C9999%2C.45%2C.40+%29 .2266 i believe

amistre64 · Answer

i got a ti83 :)  cant afford an 89 lol

anonymous · Answer

Thanks for the help.  Currently trying to figure out how to do on calc

amistre64 · Answer

might be under home

amistre64 · Answer

http://answers.yahoo.com/question/index?qid=20070918160009AAr6Q8b this one says under apps

anonymous · Answer

How would we do it from just the table alone?

amistre64 · Answer

determine the "z"

z = (.75 - .45)/.40 = .7500

and depending on how your table is set up this can go a few ways

amistre64 · Answer

do you know if your z is measured from the middle (the mean) of from the left end?

anonymous · Answer

Left end

anonymous · Answer

Ok I think i got it.  .75 on the table corresponds to .7734.  1-.7734=.2266

amistre64 · Answer

ok; the z score itself is read:

0.70  on the left side; and .05  on the top; and where they cross at is your "area" covered to the left

amistre64 · Answer

yes

anonymous · Answer

Thanks :)

amistre64 · Answer

.05
                      |
                      |
0.70 -----  .7734


area to the left of .75:  .7734


area to the right is:  1 - .7734


your welcome :)