Assume the readings on thermometers are normally distributed with a mean of 0C and a standard deviation of 1.00C. Find the probability that a randomly selected thermometer reads between -2.24 and -1.38.
The probability is =

- anonymous

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- amistre64

and your thoughts?

- amistre64

we are given a low value, a high value, a mean, and a deviation
what function have we used that has these for inputs?

- anonymous

By trying to find the area to the left of z?

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## More answers

- anonymous

INVNORM?

- amistre64

we have covered this before, its may be useful to make notes ....

- anonymous

I agree ugh sorry

- amistre64

how do we find the area between high and low values?
the inverse of this operation defines a z score, we already have z scores so the invnorm function isnt going to be useful to us.

- anonymous

normalcdf?

- amistre64

thats the one
and how do we input the information?

- anonymous

Annnd thats what I forgot :(

- amistre64

try to recall, what would you say is the most reasonable ?

- anonymous

normalcdf(-1.38,-2.24,0,1)

- amistre64

good effort, 0,1 is in the right spots
but low,high is off
-2.24 is to the left of -1.38, since its less than -1.38

- amistre64

inputs are in order: low, high, mean, deviation

- amistre64

you can try it as high, low .. it might say you did an error tho :)

- anonymous

Ok, I'll try now

- amistre64

the wolf takes the syntax: P((-2.24-0)/1

- anonymous

Ok, so I tried Normalcdf(-1.38,-2.24,0,1) and it didn't work

- amistre64

now swap the high and low about
Normalcdf(-2.24,-1.38,0,1)
that should work out

- anonymous

Ugh nope. Not that either... What am I doing wrong? Should it be Normalpdf?

- amistre64

pdf isnt valid here.
and i cant be sure that youve hit the buttons correctly :)

- amistre64

assuming you eventually get the hang of it, it shold give you a solution similar to this
http://www.wolframalpha.com/input/?i=P%28-2.24%3Cz%3C-1.38%29

- amistre64

CDF means: cumulative distribution function
we are finding the sum of the area between 2 points, is a cumulative sum so we use the CDF function

- anonymous

So it would then be 0.07 for the probability? How can I get into Wolfram? (For free)

- amistre64

PDF is a probability distribution function, and it relates to a single point ... ive never had a need to use the PDF function

- anonymous

Or 0.071 I can't figure out the rounding..

- amistre64

i use the wolf for free all the time ...

- amistre64

what do you have to round to? what number of deies?

- amistre64

** decies

- anonymous

Hmmm for some reason it never lets me. Maybe I just don't know how to find what I am trying to input and look for I guess

- anonymous

Four decimal places as needed

- amistre64

the syntax can be daunting i agree. its taken me a few years to learn the little I have for it

- anonymous

Ok figured it out on my ti83 and I got -.071247

- amistre64

then 2 or 3 decies is not appropriate ..
07120 < 07124 < 07130
4 6
we are closer to 0712

- anonymous

I make that into a positive right?

- amistre64

the negative is bad lol ... ignore that sign

- amistre64

most likely your high,low values are mixed around.

- anonymous

Ok lol! Thank you!!!

- amistre64

yep

- anonymous

I have plenty more that I still have that I am still confused about so you'll probably see me on here quite a bit

- amistre64

as long as you can recall what it is we need to use, and if im about, ill try to guide your efforts

- anonymous

Thank you so much

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