# Z Test with unknown sample size

#### Psycmajor17

##### New Member
How would I conduct a z test when I don't have "n"? The instructor never went over what to do without an "n". It has always been provided. Please help me!

The national norm for fifth graders on a standardized test of scientific literacy is 37 (σ = 3). Mrs. Jackson determines that the mean score in her class of fifth graders is 43. Can Mrs. Jackson say that her class performed above the national average? Test the appropriate hypothesis to help out Mrs. Jackson.

#### ricardo.l

##### New Member
How would I conduct a z test when I don't have "n"? The instructor never went over what to do without an "n". It has always been provided. Please help me!

The national norm for fifth graders on a standardized test of scientific literacy is 37 (σ = 3). Mrs. Jackson determines that the mean score in her class of fifth graders is 43. Can Mrs. Jackson say that her class performed above the national average? Test the appropriate hypothesis to help out Mrs. Jackson.
I think you're talking about calculating the z-score. For that you use:

z = (x – μ) / σ

z=(43-37)/3

z=2

The z score tells you how many standard deviations from the mean your score is. In this example, Mrs' Jackson's students' score is 2 standard deviations above the mean.

So, Yes, Mrs. Jackson can proudly say that her class performed above the national average

#### Camryn64

##### New Member
I think you're talking about calculating the z-score. For that you use:

z = (x – μ) / σ

z=(43-37)/3

z=2

The z score tells you how many standard deviations from the mean your score is. In this example, Mrs' Jackson's students' score is 2 standard deviations above the mean.

So, Yes, Mrs. Jackson can proudly say that her class performed above the national average
nice.. you solved beautifully