Statistics

Question 1

Why results from biology experiments often dont give clear cut patterns

3

Answer 1

1. Biological material is intrinsically variable- different genes and environments
2. Often working with small possibly unrepresentative samples of a population
3. Some variable are very hard to control

‘Chance’ factors

Question 2

Significance of r

Answer 2

Significant result if r is high

R=1 perfect positive correlation

R=-1 perfect negative correlation

R=0 no correlation at all

Question 3

4 steps for statistical test

Answer 3

1. Decide which stats test is appropriate
2. Write down null hypothesis to test
3. Use the stats test to calculate a number- the statistic
4. Evaluate the number using tables to decide whether the statistic tells that the difference in the results could easily be down to chance- null hypothesis is accepted- or whether there is a significant difference in results

Question 4

Correlation between 2 variables

Answer 4

Correlation co efficient

Question 5

Counting things in different categories

Answer 5

Chi squared test

Question 6

Two sets of measurements to compare to see if means are different

Answer 6

T test

Question 7

Null hypothesis

Answer 7

There is no significant difference between ____ and _____ . Any difference is due to chance.

Question 8

Degrees of freedom T test

Answer 8

N1 + n2 -2

Question 9

Which column is always used

Answer 9

P=0.05

5%

Question 10

When to reject null hypothesis

Answer 10

If calculated value is greater than critical value

Less than 5% probability that difference in data were caused by chance alone

Question 11

Degrees of freedom for correlation coefficient

Answer 11

Number of pairs of measurements - 2

Question 12

Degrees of freedom for chi squared

Answer 12

Number of categories - 1