Correlation

Question 1

Define correlation

Answer 1

When 2 or more variables are measured in order to identify if there is a relationship between them

Question 2

What is a correlation coefficient ?

Answer 2

• number between -1 & +1 that represents the direction and strength of the relationship between 2 variables

Question 3

What is a case study ?

Answer 3

An in depth qualitative study on a individual/ institution

Question 4

What is a advantage of case studies ?

Answer 4

• able to offer rich , detailed insights into behaviours that have more in depth explanations compared to close- ended , quantitative methods of collecting data such as questionnaires that are briefer

Question 5

What’s a disadvantage of case studies ?

Answer 5

• small sample size causes it to be less representative of a wider population
• less generalisable
• lack external validity

Question 6

Define positive correlation

Answer 6

This means that as one variable rises so does the other ( and likewise if one falls so does the other )

Correlation coefficient is roughly 0.75 close to +1

Question 7

Define negative correlation

Answer 7

As one variable rises , the other one falls

Roughly -0.75

Question 8

Define zero correlation

Answer 8

If the correlation coefficient is 0 then the two variables aren’t linked

Eg. Students heights and average test scores

Correlation coefficient is roughly 0.01

Question 9

What is an advantage of correlational research ?

Answer 9

• does not involve controlling any variables you can do it when you couldn’t do a controlled experiment
• can give ideas for future research
• correlation can be used to test for reliability and validity

Question 10

What are some limitations of correlational analysis ?

Answer 10

• can’t establish “cause and effect” relationships - it can only show that there’s a statistical link between variables
  Variables can be closely correlated without changes in one causing changes in the other - a third variable could be involved, only s controlled experiment can show cause and effect relationships
• care must be taken when interpreting correlation coefficients - high correlation coefficients could be down to chance

Question 11

Define distributions

Answer 11

Graphs plotted to represent the average and spread of some characteristics of the population

Question 12

What is a normal distribution ?

Answer 12

Symmetrical about the mean

This symmetry means that the mean , median and mode are all the same

Question 13

What shape should a normal curve be ?

Answer 13

The curve is symmetrical - it’s shaped like a bell with its peak at the mean

Question 14

What does the width of the curve depend on ?

Answer 14

Standard deviation

Question 15

What is a skewed distribution ?

Answer 15

When there are scores that cluster together at either end of the data

Question 16

What is a positive skew ?

Answer 16

• there is a cluster of scores at the lower end of the data set
• the curve has a rail on the right side of the peak - said to be skewed to the right
• mode is less than the median which is less than the mean
• eg. Reaction times , the number of children in a family , and income

Question 17

In positively skewed distributions what is bigger mode, median or mean ?

Answer 17

Mode < median < mean

Question 18

What is a negative skew data ?

Answer 18

• there are more scores at the higher end of the data set
• the tusk is in the left side of the peak - it is skewed to the left
• more is more than the median which is more than the mean
  Mode > median > mean
• negative skew is less common but an example is age at retirement

Question 19

Linear correlation

Answer 19

A systematic relationship between Co-variables that is defined by a straight line

Question 20

Scattergram

Answer 20

A graphical representation of the association/ correlation between 2 sets of scores