Normal Distibution Curve and Z scores

Question 1

Standard deviation is a measure of _____

Answer 1

spread

Question 2

Spread gives us an idea of _____

Answer 2

Variation e.g. are people at extremes or scoring very similarly?

Question 3

In a normally distributed curve, the peak of distribution is the same value as the ______, _______ and ______.

Answer 3

mean, median, mode

Question 4

In a normal distribution curve what do the numbers along the bottom represent?

Answer 4

They represent how many standard deviations away from the mean that point is (rather than measurement units.

Question 5

The further away from the mean you go…..

Answer 5

The fewer people there are

Question 6

Name the 2 properties of the normal distribution curve.

Answer 6

Symmetrical

Perfect (irl it’s messier!)

Question 7

How many scores are between 0 and -1 SD?

Answer 7

34.13%

Question 8

What is a z score?

Answer 8

A z score is how many SDs someone is away from the mean.

Question 9

__ SD away from the mean is quite a common score, however __ SDs away from the mean is quite unusual.

Answer 9

1

2

Question 10

What percent of scores lie beyond +2 SD?

Answer 10

2.28%

Question 11

What percent of scores lie within 1.96 SD ( between -1.96 and +1.96) of the mean?

Answer 11

95%

Question 12

On the z score table what does A stand for?

Answer 12

the z score

Question 13

On the z score table what does B stand for?

Answer 13

the area between the mean and the Z score.

Question 14

On the z score table what does C stand for?

Answer 14

the area beyond Z.

Question 15

If the area between the mean and the Z score is 9.10 what does this mean?

Answer 15

9.10% of the scores are between the mean and the z score.

Question 16

If the area beyond Z is 40.90 what does this mean?

Answer 16

40.90% of the scores are higher than the z score.

Question 17

On the z score table why are there only positive values?

Answer 17

because the graph is symmetrical so it’s the same either way :)

Question 18

How do you calculate a Z score?

Answer 18

z = (score-mean) / SD

Question 19

Calculate the Z score:
Mean is 150
SD is 15
James’ Score is 128

Answer 19

(score - mean)/SD

128-150/ 15 = -1.47

Question 20

What does a negative z score mean?

Answer 20

It means it is below the mean instead of above.

Question 21

James’ Z score is -1.47. The area beyond Z is 07.08, what does this mean?

Answer 21

This means that 7.08% of people scores lower than James’ score.

Question 22

James’ Z score is -1.47.
The area between mean and Z = 42.92.
What percentage of people scored above James?

Answer 22

42.92 + 50 = 92.92% scored above poor james :(

Question 23

What can you use z scores to do which is quite useful?

Answer 23

You can use z scores to compare scores that cannot be directly compared i.e. if they are on different scales.

Question 24

What is the magic number for z scores?

Answer 24

1.96!

95% of all scores within 1.96 DS of mean (between -1.96 and +1.96

Question 25

A _____ expresses how far a score is from the mean, in terms of standard deviations.

Answer 25

Z score

Question 26

What does a positive Z score mean?

Answer 26

It is above the mean

Question 27

What does a negative Z score mean?

Answer 27

It is below the mean.

Question 28

Using Z scores what 2 things can we do?

Answer 28

1. we can find out what percentage of people scores above or below and individual’s score.
2. we can compare scores on different measures.