Standard Deviation

Find the Z-score.

Mean = 22

Standard Deviation: 3.1

x = 29

• 2.26

• 16.45

• -2.26

• 1.26

Find the z-score value corresponding if the location is below the mean by 2 standard deviations

• +2.00

• -2.00

• +1.25

• -1.00

If heights of 3rd graders follow a normal distribution with a mean of 52 inches and a standard deviation of 2.5 inches, what is the z score of a 3rd grader who is 47 inches tall?

• -5

• -2

• 2

• 5

Adam's Z-score on a test is +2.50. What does this mean?

• Adam's score has a 2.5% chance of being better than any other randomly selected score.

• Adam's test score was better than 25% of his peers.

• He scored 2.5 standard deviations above the average.

• He did terrible.

Which of the following is a formula that describes calculating a z-score?

• Z = (score - mean) / stand. devation

• Z = (mean - score) / stand. dev.

• Z = score/stand. dev/ mean

• Z = dragonball

Scores on a certain standardized test have a mean of 500, and a standard deviation of 100. What score would you need to fall at the 84th percentile?

• 84

• 400

• 500

• 600

The Floppy Disk Company makes 3.5 inch floppy disks for disk drives that are 3.7 inches wide. The size of a manufactures disk is normally distributed with a standard deviation of 0.1 inches. The company manufactures 1000 disks every hour.

In one hour, how many disks would you expect to be between 3.4 inches and 3.7 inches?

• 819 disks

• 23 disks

• 500 disks

• 0 disks

Standard deviation tells us how spread out a symmetric distribution is. 
Since a Z-score tells us how many standard deviations away from average something is, what does a high Z-score mean?

• It's way higher than average

• tl:dr

• you're in trouble?

• you need a doctor

Adam's Z-score on a test is +2.5.  What does this mean?

• He'd better start studying.

• He did better than EVERYONE.

• He scored 2.5 standard deviations above the average.

• He did terrible.

Joanne's Z-score is -1.5.  What does this mean?

• She didn't take the test yet.

• She scored 1.5 standard deviations below the average.

• She did better than most people.

• No clue