Monday

September 22, 2014

September 22, 2014

Posted by **Devon** on Monday, September 10, 2007 at 7:24pm.

A. Find the number z such that the proportion of observations that are less than z in a standard Normal distribution is 0.8.

B. Find the number z such that 35% of all observations from a standard Normal distribution are greater than z.

i have now idea what they are asking, any help?

- Statistics -
**MathGuru**, Tuesday, September 11, 2007 at 9:16amIt helps to know how to read a z-table to answer these kinds of questions.

For part A, you will need to find a z value where 80% is below the z and 20% is above the z. Remember that the mean divides the distribution in half: 50% is below the mean and 50% is above the mean. Therefore, 80% is above the mean and you will have to look within the table at .30 (most tables go out to 4 places after the decimal point, so the table might show .3000) or closest to that value to find the z if your table shows from mean to z values. Tables can be set up differently, so be mindful of that when you look for these values.

For part B, you will need to find a z value where 65% is below the z and 35% is above the z. Therefore, in a table that shows from mean to z values, you will look for .15 (or .1500) in the table to find the z.

Both z values will be positive because they are above the mean of the distribution. (Negative z values are below the mean of the distribution.)

I hope this will help.

- Statistics -
**Jasmin**, Sunday, September 16, 2012 at 2:06pmFind the number z such that 35% of all observations from a standard Normal distribution are greater than z

**Answer this Question**

**Related Questions**

statistics - find the number z such that the proportion of observations are less...

Stats - Find the number z (± 0.01) such that the proportion of observations that...

statistics - Find the number z that satisfies the proportion of the observations...

statistics - The respiratory rate per minute in newborns varies according to a ...

statistics - Find the number z (± 0.01) such that 46% of all observations from a...

statistics - A population forms a normal distribution with a mean of sigma=75 ...

Statistics - What is the lowest z-value for the highest 2% of observations on ...

Statistics - What is the highest z-value for the lowest 10% of observations on ...

statistics - Using the standard normal distribution, find the probability that z...

Statistics - Using the standard normal distribution tables, the area under the ...