# Statistics

posted by .

Standard Normanl Drill:
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 -

It 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 -

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

## Similar Questions

1. ### statistics

find the number z such that the proportion of observations are less than z in a standard normal distribution is 0.8
2. ### statistics

Find the number z (± 0.01) such that 46% of all observations from a standard Normal distribution are greater than z:
3. ### statistics

Find the number z that satisfies the proportion of the observations in a standard normal distribution less than z is 30%?
4. ### Stats

Find the number z (± 0.01) such that the proportion of observations that are less than z in a standard Normal distribution is 0.8 Find the number z (± 0.01) such that 59% of all observations from a standard Normal distribution are …
5. ### Statistics

What is the highest z-value for the lowest 10% of observations on the standard normal distribution?
6. ### Statistics

What is the lowest z-value for the highest 2% of observations on the standard normal distribution?
7. ### statistics

The respiratory rate per minute in newborns varies according to a distribution that is approximately Normal with mean 50 and standard deviation 5. The proportion of observations from a standard Normal distribution that take values …
8. ### Statistics

What is the lowest z-value for the highest 2% of observations on the standard normal distribution?
9. ### Statistics

What is the lowest z-value for the highest 2% of observations on the standard normal distribution?
10. ### Statistics

Find the number x such that the proportion of observations that are less than x in a Normal distribution with mean 100 and standard deviation 25 is 0.3. (Use 2 decimal places.)

More Similar Questions