Topic 1: Data skills

Question 1

Correlation definition (1 point)

Answer 1

1. A change in one variable is accompanied by a change in another variable, but one does not cause the other to change.

Question 2

Causation definition (1 point)

Answer 2

1. a change in one variable is responsible for a change in another variable.

Question 3

What to do when it says “describing” in a question (1 point)

Answer 3

say what you see (no biological {explanation/theory} needed)

Question 4

What are the 2 ways of describing the {trend/relationship}? (2 points)

Answer 4

1. As the (x-axis/factor) increases, the (y-axis factor) increases (positive correlation).

OR

2. As the (x-axis factor) increases, the (y-axis factor) decreases (negative correlation).

NOTE: Copy the two variables IN FULL exactly as they appear on the graph axes or in the table headings.

Question 5

linear definition (1 point)

Answer 5

1. straight line

Question 6

non-linear definition (1 point)

Answer 6

1. {not a straight line / curve}

Question 7

If there is more than one {line /curve}, what should you comment on? (4 points)

Answer 7

1. GENERAL TREND
   - all may {increase/decrease}
   - all but one may {increase/decrease}
2. which line shows the GREATEST {increase/decrease} or SMALLEST {increase/decrease}? (usually not a mark for both)
3. look for SIMILARITIES between two lines – say which ones and where
4. look for DIFFERENCES - comment on the UNUSUAL line if there is onethat is different from the others

Question 8

Range bars (error bars) give an idea of the spread of data and the smaller the bars, the more _______ the data.

If there are range bars on a graph you should comment on them.

An alternative to range bars is standard deviation. Standard deviation can be calculated and given next to the data.

Answer 8

reliable

Question 9

What should you say on exam papers if range bars overlap? (1 point)

Answer 9

1. {SD/range/error bars} overlap, so there is no significant difference between data sets.

Question 10

What should you say on exam papers if range bars do not overlap? (1 point)

Answer 10

1. {SD/range/error bars} do not overlap, so there is a significant difference between data sets.

Question 11

Describing data checklist

8 points

Answer 11

1. Trend/relationship – in correct format
2. Positive or negative correlation?
3. Linear or non-linear increase/decrease?
4. Manipulate data
5. Greatest increase/decrease?
6. No constant trend – divide up line using numbers on x- axis
7. If compare two/many data sets – comment on similarities and differences (many - often there is one line which is different from the rest)
8. If range/SD bars or SD in tables – look for overlap, no significant difference in data sets. If no overlap, there is a significant difference in data sets.

Question 12

what does it mean when a question says “analyse data” (1 point)

Answer 12

1. describing data

Question 13

How do you calculate rate of change? (1 point)

Answer 13

Change in y over change in x

change in y / change in x

Question 14

How do you calculate percentage change? (2 steps_

Answer 14

(previous value) - (current value) = (difference)

difference
============== X 100 = (change)%
(previous value)