2. Experiment 1
Investigating the effect of temperature on the rate of respiration of Crustae larvae.
Basic expt: Measure the respiration rate of larvae at 3oC then every 3 degrees up to 18oC. See results on next page.

3. Effect of temperature on the respiration rate of Crustacea Larvae
State null hypothesis
Which stats test? Give a reason.
Calculate test statistic and explain what this shows.
Temp ° C
Respiration. rate.μg O2 h-1 3
0.12 6
0.17 9
0.15 12
0.21 15
0.22 18
0.35

4. Check your answers: Null hypothesis:
There is no significant correlation between a change in temperature and the rate of respiration. Or
The temperature does not effect the rate of respiration.

5. Which stats test with reason:
Reason: You are looking for a correlation between a change in temperature and the rate of respiration

6. Calculating and interpreting test statistic.

8. Rs = x ( ) = = =
(6x6x6) –

9. Interpreting the test statistic:
State what it shows:
My value of is greater than 0.89 which is the critical value for 6 pairs of measurements P < 0.05
Explain the probability of your results being significant:There is less than 5% probability the correlation between temperature and respiration rate is due to chance
Accept or reject your null hypothesis
I reject my null hypothesis

10. Experiment 2
Investigating the growth of Pleurococcus on the north and south facing sides of tree trunks.
Basic expt: Measure the coverage of Pleurococcus on the north and south facingtrunks of a tree. Repeat the experiment 14 more times.

11. Which stats test? Give a reason.
Pleurococcus coverage on north facing tree trunk / cm2
Pleurococcus coverage on south facing tree trunk / cm2 28 6 36 21 27 35 34 25 43 73 63 16 8 12 7 26 45 18 67 32 58 13 39 19 62 5
State null hypothesis
Which stats test? Give a reason.
Calculate test statistic and explain what this shows.

12. Check your answers: Null hypothesis:
There is no significant difference in the coverage/amount of Pleurococcus on the north and south facing sides of tree trunks. Or
The direction the trunk faces does not effect the amount of Pleurococcus.

13. Which stats test with reason:
Reason: You are looking for differences in the mean coverage of Pleurcoccus on the north and south facing sides of the trunk

14. Calculating and interpreting test statistic.

15. Pleurococcus on North side Pleurococcus on South side
Mean 613 = 40.87 15
Sd = 18.01
SE = 18.01
√15
3.873
SE = 4.65
Mean 348 = 22.6 15
Sd = 15.14
SE = 15.14
√15
SE = 15.29
3.873
SE = 3.909

16. Pleurococcus on North side Pleurococcus on South side
SE = 4.65
2 X SE = 9.3
95% confidence limits =
Mean + 2 SE = = 50.17
Mean – 2 SE =
40.87 – 9.3 = 31.57
ie to 55.04
Draw a graph of the mean
and show the 95% confidence limits on to it
SE = 3.909
2 X SE = 7.818
95% confidence limits =
Mean + 2 SE = =
Mean – 2 SE =
22.6 – =
ie to
Draw a graph of the mean
and show the 95% confidence limits on to it

17. Use of Standard Error in showing 95% Confidence Limits on a bar chart of Mean Values
Show 2 SE value up from the mean and show 2 SE value downwards from the mean for each bar. This illustrates the range for the 95% confidence Limits for each mean value.
Mean Coverage of Pleurococcus / cm2
- 2 S.E
North facing
South facing
Side of tree

18. Interpreting the test statistic:
State what it shows:
The error bars do not overlap.
Explain the probability of your results being significant:
There is less than 5% probability the difference in the mean coverage on the north and south sides is due to chance.
Accept or reject your null hypothesis
I reject my null hypothesis

19. Experiment 3
Investigating the distribution of banded snails in the environment
Basic Expt.: Count the number of banded snails in 1m2 of hedgerow then repeat in 1m2 of grassland.

20. Which stats test? Give a reason.
State null hypothesis
Which stats test? Give a reason.
Calculate test statistic and explain what this shows.
Number of snails in 1m2 hedgerow
Number of snails in 1m2 grassland 24 12

21. Check your answers: Null hypothesis:
There is no significant difference between the number of snails in a hedgerow and the number of snails in the grassland. Or
The type of area has no effect on the number of snails.

22. Which stats test with reason:
Reason: You are looking for a difference in the number of snails in particular categories.

23. Calculating and interpreting test statistic.

24. Hedgerow 24 18 6 36 2
grassland 12 18 -6 36 2

25. Calculating and interpreting test statistic.
= = 4

26. Interpreting the test statistic:
State what it shows:
For 1 degree of freedom the critical value is My value of 4 is greater than the critical value so P < 0.05
Explain the probability of your results being significant: significant:There is less than 5% probability the difference in number of snails in each area is due to chance
Accept or reject your null hypothesis
I reject my null hypothesis