t tests

Statistics

Whelks

Tomatoes

Asellus

Hypothesis

There is no difference in the height of shells from sheltered and exposed shores.

Hand pollinated and sprayed plants set the same amount of fruit.

Gill movement is not correlated with the oxygen content of the habitat.

Compared groups

Sheltered

Exposed

Sprayed

Pollinated

Stagnant

Oxygenated

Mean (x)

30.42

20.50

46.60

57.60

49.14

44.30

Standard deviation (s)

4.87

3.09

14.30

13.52

4.45

3.23

Sample size (n)

12

12

10

10

7

10

Standard error (s.e.)

1.41

0.89

4.52

4.27

1.68

1.02

95% confidence limit

2.81

1.78

9.04

8.55

3.36

2.05

Lower 95% confidence interval

27.60

18.72

37.56

49.05

45.78

42.25

Upper 95% confidence interval

33.23

22.28

55.64

66.15

52.51

46.35

t statistic

5.96

1.77

2.46

Degrees of freedom

22

18

15

Critical values (tcrit)

2.07

2.10

2.13

Significant?

Yes (5.96 > 2.07), sheltered shells are significantly taller.

No (1.77 < 2.10), sprayed and hand-pollinated plants set the same amount of fruit.

Yes (2.46 > 2.13), there is more gill activity in stagnant water.