Statistics

[School_girl]

For a Normal(0,1) density, find the 1% upper critical value z .01. How do you do this problem??

 

[tkhunny]

Look it up in a table.
Get your calculator to tell you.

There isn't an easy way.

Do you have a book? Surely there is a table of values for the Standard Normal Distribution in the back.

 

[wjm11]

For a Normal(0,1) density, find the 1% upper critical value z .01. How do you do this problem?

One way is just to use the table in your book. Do you know/understand what z is? Basically, it's just the number of standard deviations that a given value is above or below the median. Tables in various books can be presented a few different ways, so I can't tell you exactly how to read the table you have, but here goes. You might have one table for positive z values and another for negative z values. Use the one for positive z values (for values greater than 50%, i.e., for values above the median). Locate ".9900" (99%) in the table. The number to the far left of the .99 plus the number at the top of the .99 column is your z value. It should be a little under 3.

Alternatively, if your positive z table only goes up to .5, it means you need to add these values to .5 (50%). So 99% is represented by .4900 in the table.

I hope this helps.

 

[School_girl]

I know how to find Z.01, but I don't know the 1% upper critical value Z.01. Can you explain this 1%?

 

[tkhunny]

Do you have a book? If you do, there is a table in the back. When you find it, it will have a little picture of a Standard Normal Curve. It will be one of two varieties:

1) It will have a tail region shaded. Find the value of 1% in the table.
2) It will have a central region shaded, leaving the tail blank. Find the value of 49% on one side.

It's just a matter of understanding the table.

This has a cool calculator.

http://www.psychstat.smsu.edu/introbook/sbk11m.htm

Or, the Quantile Applet is neat. Type in 0.99 0.00 and 1.00

http://www-stat.stanford.edu/~naras/jsm ... ility.html