Correlation and Distribution

Question 1

what are scatterplots used to display?

Answer 1

relations between two quantitative variables

Question 2

positive relationship

Answer 2

both variables increase

Question 3

negative relationship

Answer 3

variables change in opposite directions

Question 4

strong relationship

Answer 4

points lie close to a line

Question 5

weak relationship

Answer 5

points are widely scattered

Question 6

perfect relationship

Answer 6

often appears when cheating has occurred, or when the same thing is being measured

Question 7

what is the purpose of correlational analysis?

Answer 7

• determine whether there is a linear relationship between variables
• the direction and strength of relationships

Question 8

pearson correlation coefficient

Answer 8

r

Question 9

spearman correlation coefficient

Answer 9

rs

Question 10

what do correlations make no distinction between?

Answer 10

the IV and DV

Question 11

how can linear relationships be measured?

Answer 11

by correlations

Question 12

correlations and non-linear relationships

Answer 12

correlations cannot be used, and data may need to be transformed

Question 13

pearson correlation

Answer 13

• calculated directly from the raw score
• suitable for interval or ratio data
• highly affected by outliers
• not suitable for skewed data

Question 14

spearman correlation

Answer 14

• calculated from the ranking of the raw scores
• suitable for ordinal data
• marginally affected by outliers
• suitable for skewed data

Question 15

issues with sample size

Answer 15

small samples can indicate a pattern when there is no real relationship

Question 16

when are density curves useful?

Answer 16

when dealing with lots of data, that can be distributed normally and generalised to the population

Question 17

what do density curves use?

Answer 17

a mathematical model to describe a histogram distribution of scores

Question 18

_______ and _______ ______ should be ignored

Answer 18

outliers, extreme values

Question 19

normal distribution

Answer 19

perfectly skewed data

Question 20

positively skewed data

Answer 20

right f

Question 21

negatively skewed data

Answer 21

left f

Question 22

what do density curves display?

Answer 22

the overall pattern of a distribution, as all the data is under the curve

Question 23

when can predictions be made for distribution?

Answer 23

if certain values of the model are known, e.g., mean or SD

Question 24

what can normal distributions be used to describe?

Answer 24

lots of naturally occuring data that is distributed similarly around a single measure of central tendency

Question 25

what can observed data be fit to?

Answer 25

the normal curve

Question 26

how can distributions be described?

Answer 26

using different parameters of mean and SD

Question 27

mean of the sample

Answer 27

x̄

Question 28

mean of the population

Answer 28

μ

Question 29

SD of the sample

Answer 29

S

Question 30

SD of the population

Answer 30

σ

Question 31

what is normal distribution described by?

Answer 31

a normal curve
- symmetrical, single-peaked, and the tail meets at the x-axis at infinity
- the higher the mean, the further along the axis it is
- shape is determined by SD

Question 32

what do statistical tests assume?

Answer 32

data is normally distributed

Question 33

what happens if data is not normally distributed?

Answer 33

parametric tests must be used

Question 34

what do standard scores allow us to do?

Answer 34

compare values from different datasets

Question 35

how can different datasets by translated into a standard normal distribution?

Answer 35

they can be standardised by calculating z-scores

Question 36

z-score

Answer 36

(deviation of x from mean) / standard deviation

(x - x̄) / S

Question 37

what is the z-score

Answer 37

the number of standard deviation that the observation deviates from mean

Question 38

what is created when z-scores are plotted?

Answer 38

a normal distribution

Question 39

mean and SD of z-score

Answer 39

mean = 0
SD = 1

Question 40

mean and SD of standard normal distribution

Answer 40

μ = 0
σ = 1

Question 41

how are normal datasets standardised into standard normal distributions?

Answer 41

by calculating the z-score

Question 42

what does the area under the standard normal distribution curve represent?

Answer 42

the percentage of participants (100%) and equals 1

Question 43

what does the table entry indicate?

Answer 43

the area under the curve to the left of the line