How Science Works

Question 1

Why is there a control variable in an experiment?

Answer 1

• To provide a value to compare the results of the experiment to
• To determine that any change in the dependent variable is directly caused by the changes to the independent variable

Question 2

How is a control group treated?

Answer 2

Treated the same/fake drug administered in the same way. Given a fake drug/saline water.

Question 3

What is the independent variable?

Answer 3

The thing that is changed

Question 4

Where are the results for the independent variable placed`?

Answer 4

On the x-axis

Question 5

What is the dependent variable?

Answer 5

The thing that is measured

Question 6

Where are the results for the independent variable placed`?

Answer 6

On the y-axis

Question 7

What is the control variable?

Answer 7

The thing that is kept the same

Question 8

Why are the percentages/rates/ratios used?

Answer 8

Allows comparison between results as they have different starts (e.g. starting mass/birth rates/population sizes)

Question 9

How is correlation and causation explained?

Answer 9

1) Say if there is a negative/positive correlation
2) Even with correlation this does not mean causation
3) Could be due to another factor (give example)
4) State the points that do not fit the pattern

Question 10

How is the validity of the results explained?

Answer 10

• What may have affected the accuracy of the results? e.g. sample size, appropriate temp/conc/time, repeats, standard deviation
• Look for results that do not fit the pattern and quote them

Question 11

How do you avoid bias in an experiment?

Answer 11

Make sure that everything is random and avoid personal opinion in the conclusion.

Question 12

How do you evaluate an experiment?

Answer 12

• Describe the positive and negative aspects of the experiment.
• Say what support the conclusion and what doesn’t
• Quote data

Question 13

How do you describe the results of an experiment?

Answer 13

• Say what you see and quote figures

Question 14

How do you explain the results of an experiment?

Answer 14

Say why something has happened in detail with key terms.

Question 15

Why is the mean value used?

Answer 15

Allows comparison with different samples

Question 16

How are unknown values found?

Answer 16

• Plot known variable
• Draw line of best fit
• State where you would extrapolate data from

Question 17

What is the standard deviation and what can this tell us about the results of an experiment?

Answer 17

• Spread of the data around the mean
• If they overlap there is no real difference between the results
• If they don’t overlap then there is a real difference between the results

Question 18

How is the probability of chance used to explain results?

Answer 18

• If there is a real significant difference there is less than 5% probability that the results are due to chance.

Question 19

How is the percentage uncertainty found?

Answer 19

• Smallest division of measuring instrument divided by half then divided by value measured

Question 20

What is mean by high precision?

Answer 20

Results are spread close to the mean.

Question 21

What is meant by a repeatable results/experiment?

Answer 21

The original experimenter repeats the investigation using the same methods and equipment and gets the same results.

Question 22

What is meant by reproducible results?

Answer 22

If the investigation is repeated by another person, or by using different equipment or techniques, and the same results are obtained.

Question 23

When is a logarithmic scale used?

Answer 23

When using really big scales or ranges

Question 24

How is the percentage change calculated?

Answer 24

(Change/orginal) x 100

Question 25

What is meant by accuracy?

Answer 25

If the values obtained are close to the true value

Question 26

How is accuracy increased?

Answer 26

• Carry out more tests around the estiamted value to make interval smaller
• Repeat each test

Question 27

When is a t-test used?

Answer 27

Looking at differences between two means

Question 28

How do you know if results of t-test are significant?

Answer 28

The probability is less than 5% that the results are due to chance

Question 29

When is a spearman’s rank used?

Answer 29

Looking for a correlation between two sets of continuous data.

Question 30

What do the spearman’s rank results state?

Answer 30

value of + = positive correlation
- = neagtive correlation

1 = perfect correlation
0 = no correlation

Question 31

When is a chi-squared test used?

Answer 31

When looking at frequencies of categoric data with the same dependent variable

Question 32

What are rules for scientific drawings?

Answer 32

• No sketching/hanging lines/shading/cross lines
• Give the scale
• Draw on the left and label on the right (with straight lines)