Evaluations in Biology

Question 1

How do you calculate standard deviation?

Answer 1

• Calculate mean of all values. (e.g. 59)
• Find difference between each value and the mean (e.g. 62 - 59 = 3)
• Square each difference (e.g. 3 squared = 9)
• Add all these square numbers (minus numbers = positive numbers)
• Divide this number by (number of values - 1).
• Square root that number to find standard deviation.

Question 2

What does standard deviation do?

Answer 2

Measures the spread of data around the mean value.

Question 3

How to make test more reliable.

Answer 3

• Repeat experiment.
• Calculate mean.
• Identify anomalies.

Question 4

How to make test more accurate.

Answer 4

• Carry out more tests within existing range.

- Use narrower range if appropriate.

Question 5

How to increase validity of experiment.

Answer 5

• Make sure equal volumes used each time.

- Make sure equal concentration used each time.

Question 6

Why is a control used?

Answer 6

• Allows a comparison to be made

- Shows what would normally happen so comparison can be made when independent variable is changed.

Question 7

When answering describe questions…

Answer 7

• Write what the data is showing e.g. trends, changes in rate, increases and decreases etc
• If describing a graph, break the graph down into sections
• Each section should be a describable feature
• e.g. constant rate from A to B, increasing rate from B to C…
• Use data points provided in the question to illustrate description.

Question 8

When answering explain questions…

Answer 8

• Say why the results have come about

- Use scientific knowledge to explain any patterns and trends

Answer 9

• Provide both positive and negative responses to the statement
• Use the data given and scientific knowledge to agree with conclusion
• Use methodological errors (e.g. no statistical test performed, small range of samples etc)