Daniel B. answered • 06/13/21
Tutor
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A retired computer professional to teach math, physics
I believe your mistake is in looking up z scores in your table.
The z scores you listed are for -3.75 and 3.75.
My table does indeed gives me the probability of 0.292, provided
I use your actually calculated z = -0.375 and 0.375.
Brian P.
I guess maybe I am confused on which chart to use. Are there 2 different z tables??
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06/13/21
Daniel B.
tutor
Wyzant does not let me give you a web link, but here is the table I used. Go to Wikipedia, and search for "Standard Normal Table". It has the table and a description of how to use it. It actually handles z values to only 2 decimal places. You need to use interpolation for the third decimal place.
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06/13/21
Daniel B.
tutor
On the Wikipedia web page there are actually three tables. For your purposes, the first table would be easiest.
That first table is actually divided into two -- one for negative and one for positive z-values. Do not let that confuse you. Just read the description at the head of the table.
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06/13/21
Daniel B.
tutor
Look up the table values for 0.37 and 0.38, and then use the average of the two. Same thing for -0.375.
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06/13/21
Brian P.
Thank You. I made an obvious glaring mistake. But, I still can not figure how to find .375?? I can find .307, but am not sure how to read the chart to find .375????06/13/21