Z-Scores

What information does a z-score give us?

• Position of a data point within a distribution relative to the mean.

• The number of pieces of data within a distribution.

• The mean of a distribution.

• The standard deviation of a distribution.

Which set of z-scores is always considered unusual?

•  $-2<z<2$  

•  $-3<z<3$  

•  $x<-2$   or    $x>2$  

•  $x<-1$    or   $x>1$  

Which z-scores are considered unusual? Check ALL that apply.

• z = 2.7

• z = 1.8

• z = -2.1

• z = 0

• z = -1.99

Tags

CCSS.HSS.ID.A.4

If a z-score is equal to zero, then the x-value and the mean of the data set are equal.

• True

• False

Calculate the z-score:

 $\mu=70$  

 $\sigma\ =\ 10$   
 $x\ =55$  

• z = -1.5

• z = 1.5

• z = 48

• z = 1.09

Calculate the z-score:

 $\mu=100$  

 $\sigma\ =\ 12$   
 $x\ =128$  

• z = 2.33

• z = 0.6875

• z = 1.16

• z = 2.05

If a z-score is positive  $x>\mu$  

• True

• False

Approximately what percent of the data fall between two standard deviations of the mean?

• 68%

• 95%

• 99.7%

• Not enough information

Tags

CCSS.HSS.ID.A.4

I am confident finding a z-core.

• I don't know how to start.

• I sometimes use the formula incorrectly.

• I think I have it but would like more practice.

• I understand and could teach someone how to find a z-score.